From Destinypedia, the Destiny wiki
The Cabal are a warmongering race of giant bipedal humanoids with a heavy-set, rhinoceros-like appearance. Their ever expanding interstellar Cabal Empire spreads through organization, efficiency, and corruption. The Cabal army that occupied Mars and held it for some time was but a fraction of their full might. During the Red War, Cabal warlord Dominus Ghaul and his Red Legion seized the Last City and the Traveler in a surprise attack. After Ghaul's demise, the Red Legion shattered into numerous warring factions across the Solar System. The exiled Emperor Calus, previously dethroned by Ghaul and later arriving onboard his spaceship, the Leviathan, presents less antagonistic attitude towards humanity and the Guardians. In recent time, Caiatl, daughter of Calus, assumed the Imperial throne and became the new Empress of the Cabal Empire.
The Cabal are an extremely tough species, willing to defend their territory until every last one of them is dead. Their architecture is very industrial, with an emphasis on burrowing into mountains for defense. They are a very industrious, militaristic species whose social structure and way of life revolves largely around conquest and expansion. Their armor and technology can often be seen leaking a substance similar to oil and even emit smoke when damaged or worn. For centuries they have devoted their resources to occupying and mining Mars, contesting with the native Vex programming as evidenced by the many Cabal ships seen bringing armies to and from the red planet, and recently dealing with the Guardians.
Interestingly, the Cabal are the only hostile race up to date that does not appear to overtly feature worship in its culture—the Fallen worship their god-like Servitors, while Hive have devoted their entire religion to the worship of the Darkness, while the Vex of the Sol Divisive revere the unknown entity that is the Black Heart—but as of the Taken War, evidence has been gathered that the Cabal revere a deity-like Emperor, later being revealed to be Emperor Calus. And at one point, they have even ruled the galaxy, and since the reformations that happened within their empire, they seek to do it again, and likely beyond.
The earliest period of the Cabal's history is the Era of Lead; before the aforementioned race had extended their reach beyond their immediate star system. According to Cabal myth, three Cabal warriors sought to claim the sun atop a great mountain that was guarded by a mighty beast. The first two were killed attempting to outwit and evade the beast, but the third died with pride and honor after challenging it to battle. Her sacrifice had left a mark upon the creature and inspired her Cabal kin to face the creature despite repeated deaths; with each leaving their scars upon the latter. Finally, the last warrior named Acrius had delivered the killing blow upon the beast which had grown wounded and weary of the constant fighting. Acrius became the first Cabal to succeed in claiming the sun, and thus united their race under his reign as the first Emperor.
The Era of Conquest came as a largely unknown period of military expansion and galactic colonialization as the Cabal extended beyond their system to incorporate many worlds and client races into their empire; most notable was the Psion race who became assimilated into Cabal society through indentured servitude but were prized for their psychic abilities. Conquered worlds were enriched with ceremonial gold to ease defeat and afford the opportunity to challenge officers for representation within the Cabal's leadership. In the earliest days of this new empire, the Cabal emperor ruled alongside the venal military aristocracy known as the Praetorate, which allowed the people to suffer so the Legions who served them could grow. The Praetorate had also popularized the Rite of Proving: an ancient tradition of gladiatorial combat for free Cabal to prove their worth in battle and ascend in status.
The rise of Calus as Emperor would mark a paradigm shift in Cabal society as he began a campaign to reorganize the empire from its militant roots into one favoring art and philosophy. Much of the empire's history (which was transcribed in the Codex of Lawful Transgressions) was rewritten by his own cult of personality to cast a more favorable light upon Calus during his ascension. He also abused the Rite of Proving by gradually introducing draconian and byzantine bylaws into the Proving; most notably the role of an arbiter wielding the Hammer of Proving whose role was abused to the point that the Rite fell out of common usage in a century.
Rise of Calus
Upon Calus's Inauguration, he had the wasteland of an unknown planet cleared of any stone or plant in order to have a desert of pure white. Three days later, a violet pavilion was constructed and Calus's court was recreated in every detail.  The first act of his coronation was to send the Consul into the wasteland as a symbol of the revolution he would soon bring. During his reign, Calus decided to purge the corrupt Praetorate and he and his imperial guard marched into the temple where the former Cabal senate convened and assassinated them.  He then granted citizenship to the various Legions and set Evocate-General Umun'arath as Primus of All Legions.
During this time, Calus moved the Capital to Torobatl so it could be closer to his people, throwing parades daily as he bought from the local marketplaces. Following his "great purge", Calus spoke to the people at Dau'uss, announcing that he had repossessed the wealth and plunder of the Praetorate elite. 
Calus's reign was not without personal troubles. He was wary of Umun'arath, his Evocate-General, for her paranoia and obsessive fixation on war. His own daughter and heir, Caiatl, grew up similarly despite his efforts.
One of Calus's pleasures was the Coliseum, and one day, an albino gladiator named Ghaul made his first appearance there. Ghaul's patient skill and unusual coloration soon made him a favorite of Calus's, and the Emperor eventually made him Primus of the Red Legion, where his talents would be put to better use. Calus grew to love Ghaul like a son and believed they were kindred spirits who both envisioned a newer, more perfect world. Ghaul's association with The Consul and members of the Praetorate worried him, but not enough.
Calus claims to have overseen a reign of glory. His Empire was an immense military power, but valued willpower, learning, gentility, and subtlety. Debate was as celebrated as warfare. Savage pit fights coexisted with precise marksmanship and refined martial arts. The Empire crafted technological marvels that allowed every need to be met and every life to be lived in comfort.
As the Cabal Empire expanded, it encountered countless alien races and absorbed them into itself: indoctrinating their species, collecting their technology, learning their knowledge, and merging with their culture. The number of species within the Cabal Empire "defied reckoning," and examples of the things they created, whether texts, tech, or superweapons, were archived in carefully maintained athenaeum worlds for study and potential future use.
Centuries after destroying the Psions' clairvoyant OXA Machine, word reached the emperor that it had been rebuilt on the moon of Brand. The Evocate-General then sent her ships to bomb the moon but Calus stopped her ships and instead proposed an alliance with Otzot, the Psion which rebuilt the machine. 
It was seemingly during Calus's reign that the Cabal learned of the Traveler and the Light, and gained some knowledge on the Darkness from the "Dreams of worms". His Empire has even defeated a Light-empowered race on at least one occasion.
However Ghaul, having grown disillusioned with Calus's reign and determined to return the Cabal to their warmongering ways, conspired with the Consul and several of Calus's closest friends and advisors: Umun'arath, Shayotet, Otzot, Moli Imoli, Iska'al, and Caiatl in a bid to usurp the Emperor. Ghaul and his Red Legion launched his coup in the dead of night, arresting Calus and his Loyalists. With the Emperor too popular to simply execute, Ghaul, his Red Legion, and the Consul sentenced Calus and his supporters to exile aboard the Leviathan, taken far from the Empire along a pre-programmed course.
Ghaul swiftly assumed power. Declaring that there would be no more emperors, he instead assumed the title of Dominus and imposed radical reforms on the Empire. Under his leadership, Cabal culture moved from hedonism and pleasure for all to militarism and personal glory. The Empire's member species were diminished in relevance. Its subtlety was replaced by brute, industrial force. It conquered rather than absorbed.
War for the Sol System
Arrival in the Solar System
The Cabal's scouting legions arrived in the Solar System at some point following the Collapse. Encountering no meaningful opposition, they established a beachhead on Phobos, constructing massive facilities such as Fleetbase Korus and Firebase Thuria before invading Mars. Their initial intention was to mine Mars for resources, but the scope greatly expanded upon discovery of the Vex ruins. The Virgo Prohibiton, the Vex collective on Mars, didn't take too well to the Cabal arrival, and so began a war that wouldn't end until The Red War.
A Ghost that had infiltrated a Cabal base on the planet took note of visible dissent among their ranks: while some remained loyal to the Empire and obeyed their ancient orders without question, others did not, and tensions between the two groups may presage a schism. It is possible that some Cabal were aware of Ghaul's coup against the Emperor, which may have been an additional source of tension, but the transmissions for this do not make it clear whether all of the Martian Cabal knew, or if they had taken any sides. One unit, the Broken Legion commanded by Valus Trau'ug, even mutinied, massacring his superiors and attacking the Reef without authorization, resulting in their capture by the Awoken. For Trau'ug's treason and failure, Cabal High Command disavowed the entire legion, leaving them in the Prison of Elders.
During the Guardians' mission to reach the Black Garden, the Guardians had to charge a Gate Lord's eye to unlock the gateway. Traveling to Mars, the Guardians breached into the Conflux to power the eye but encountered regiments of the Blind Legion, a cabal army tasked with capturing and holding Vex artifacts. Despite the Cabal's efforts, the Guardians were able to reach the main site of the Conflux and begin to charge the eye but are then confronted by the Blind Legion's commander, Primus Sha'aull. After a heated battle and despite the Primus' efforts, the Guardians were able to charge the eye and kill Sha'aull. With the eye fully charged, the Guardians were able to reach the Black Garden. With the Primus dead, the Blind Legion was without a commander; a huge blow, and one in which the Blind Legion would never recover from.
At a later date, the Vanguard received a message from the Warmind Rasputin, warning them that a trio of Psion Flayers, called the Ice Reapers, were attempting to hack its mainframe on Mars, after the Warmind used Warsats to bombard Cabal troops. Wanting to prevent the Cabal from hacking into the Warmind's data and weapon systems, the Guardians formed a strike team and battled with the Cabal through the Dust Palace located in Freehold. Reaching to the Flayers' position, the Guardians made combat with the elite Psions and their guard but despite their power, they succeeded in slaying the Psions, saving Rasputin. A huge blow to another Cabal Legion, and one that seemingly destroyed the Ice Reapers, as they were never seen again.
Wishing to take the fight to the Cabal, the Vanguard saw an opportunity to strike a blow against the Cabal when Valus Ta'aurc, the infamous commander of the Siege Dancers, was seen in his Land Tank, Cerberus Vae III, stationed in the Valley of Kings. Forming a strike team and managing to breach past the Cabal's defenses, the Guardians were able to enter the Land Tank and confront Valus Ta'aurc. After a struggle, the Guardians succeeded in slaying the Valus, dealing a critical blow to the Siege Dancers and Cabal leadership on Mars. Not only did they slay the Valus but they also slew 4 others; ending The Siege Dancers' chain of command and knocking them out of the war on Mars, along with the Ice Reapers, out of the fight.
The Taken War
Prior to the start of the Taken War, the Vanguard speculated that a new task force, a "second fleet" led by the Skyburners, was being assembled at Phobos for the purpose of invading Earth. After the arrival of Oryx, the Taken King and his Dreadnaught, however, the Cabal were forced to evacuate their Fleetbase and other sites in the system due to Taken infestations. This was a huge blow. In the ensuing battles, various detachments across Phobos and Mars suffered enormous casualties against the Taken, with the Sand Eaters losing 58% of their troops, the Blind Legion losing 35%, and the Dust Giants losing 39%. In addition, the entire local Cabal fleet was mobilized, and any ship that was not already on the move by the time The Guardian arrived on Phobos was believed to have been destroyed. With the Skyburners being redeployed to reinforce the other battered Cabal during the course of the Taken War, the campaign against Earth was temporarily placed on hold. Following this considerable setback, Primus Ta'aun, commander of the Skyburners and the mightiest Cabal in Sol, sent a report up the Cabal chain of command suggesting that the Hive technology aboard the Dreadnaught could be co-opted for Cabal use. Ta'aun also proposed any technology recovered could be used against Guardians, as the Primus had begun to realize that the Cabal battle strategy was becoming hopelessly mired in a losing attrition war with the City. His report reached Dominus Ghaul, who then ordered Ta'aun to personally board and capture the Hive vessel by any means necessary. In the aftermath of the Battle of Saturn, Ta'aun rammed his warship, the Dantalion Exodus VI, into the Dreadnaught in order to establish a beachhead. While leading a squad through the Mausoleum in an attempt to reach Oryx's ascendant realm, Ta'aun was Taken and transformed into Ta'aun, Hand of Oryx, forced to guard the entrance to the Taken King's altar where he would be slain by the Guardian.. Ta'aun's bond-brothers Valus Mau'ual and Valus Tlu'urn then ventured deep into the Dreadnaught and planted explosives at its power core, either as part of a preconceived plan to force the Hive's surrender, to avenge their lost Primus or both. If allowed to succeed, the blast would have destroyed the majority of the Solar System. Fortunately, the two Shield Brothers were stopped by a Guardian fireteam before the explosives could be detonated. With their leaders vanquished, the surviving Cabal on Dantalion Exodus VI transmitted a distress signal to the rest of the Empire. Though the Guardian disabled this signal, they were unable to prevent it from reaching its intended recipient. The remaining Skyburners on the Dreadnaught continued to fight a desperate struggle to survive as their beachhead was slowly overrun by Hive and Taken. Eventually, the remaining Skyburners were slaughtered.
Meanwhile, on Mars, the Cabal clashed with the resurgent House of Wolves, who had gathered on the red planet to heed the call of their new God-Servitor Orbiks Prime. Weakened by the casualties suffered in previous conflicts, the Cabal were unable to evict the scavengers as they took the Cabal's subterranean labyrinths for their own. The Guardians solved the problem by destroying the Servitor, leaving the Wolves broken once more.
Shortly after Oryx's defeat, a New Monarchy agent sent a report to his Executor superior which noted the depletion of Cabal leadership: the Skyburners' Primus and his bond-brothers, Primus Sha'aul, Valus Ta'aurc, Valus Trau'ug, and a large mass of lesser Vals and Bracuses all dead or heavily outnumbered. The New Monarchy believed that in the face of such staggering losses, the Cabal Empire would have no choice but to respond to the Guardians' attacks. In due time, the Cabal's response would arrive.
The Red War
Seeking the Light
Two years after the Taken War and one year after the SIVA Crisis The Cabal Empire's response would finally arrive. The Red Legion, under the command of Dominus Ghaul himself, would launch a devastating assault on the Last City which was carried out flawlessly. Taking the City by surprise, the Red Legion rapidly overwhelmed it and destroyed the Tower while his cage device latched onto the Traveler. Ghaul's forces took particular care to capture the Speaker alive, as the Dominus was interested in his connection to the Traveler. In a desperate plan to kill him, The Guardian boarded his flagship, The Immortal, and destroyed its shield generator in advance of a concentrated counterattack. This attack never materialized, and Ghaul personally stepped out to confront the Guardian. As the two faced off, the Cage activated its suppressive shield and stripped the Guardian -- all Guardians -- of their Light. With his victory assured, Ghaul beat and mocked the Guardian before kicking them off of the Immortal. Dominus Ghaul and his Red Legion had succeeded where previous forces had failed to accomplish for centuries: invading the Last City and defeating its Guardians.
Days later, aboard the Immortal, Ghaul implored the Traveler to choose him and join his empire. The Consul, in contrast, only viewed it as an advanced machine and advised Ghaul to simply seize its Light by force. Ghaul disagreed with the Consul's approach and had the Speaker brought to him, seeking to use him to gain the Traveler's approval.
In addition to conquering the Last City, he sent his prized warship, The Almighty, to the system's sun to destabilize it and cause it to go supernova should the system resist any further. His remaining forces have been sent to the European Dead Zone to hunt the remaining Guardians, to Io to mine the remaining Light energy from the Traveler and to Nessus to study the Vex. Ghaul also sent a powerful force to Mars to reinforce the Cabal forces there, finally driving the Vex from Meridian Bay and destroying the portal to the Black Garden, destroying most of the Virgo Prohibition, and all other places in the solar system.
For a time, the Red Legion maintained complete control of the Solar System but a few Guardians were able to regain control of their Light from interacting with a Shard of the Traveler in the European Dead Zone. In doing so, they began to fight back against the Red Legion, humiliating their forces. At first, the guardians conducted minor operations such as scouting and analysis. These operations would soon advance into the theft of Legion supplies, and the assassination of their leaders. Soon after, the Legion firebase is disabled, with further operations being carried out. Gathering the Remnants of the Vanguard, the Guardians planned an organized attack to reclaim the Last City preceded by the disabling of the Almighty. Despite the loss of their Light, the Vanguard Leadership launched the attack to reclaim the Last City. As this occurred, the Guardian was tasked with boarding the Almighty and permanently disabling the superweapon. After eliminating the threat of the Almighty, the Guardian heads back to Earth to join the fight. Hearing of both the attack and the loss of the Almighty, the Consul angrily demanded Ghaul take the Light from the Traveler and destroy the Guardians. The Dominus, however, remained adamant that he needed to prove his worth to be chosen by the Traveler. In his rage, the Consul released the weakened Speaker and ranted that Ghaul had already been chosen, not by the Traveler but by the Consul, the day he found him as an orphan and raised him to be the warrior who would deliver their people and promise him vengeance. Convinced by this argument but angered by the Consul's arrogant insubordination, Ghaul killed his old adviser while swearing to take the Light by force.
At the top of his warship near the Traveler's Cage, Ghaul faces off against the Guardian he previously defeated once more, this time infused with some of the Traveler's Light, granting him similar abilities to the Guardians. However, the Light that was bestowed upon him was corrupted as he was not chosen like the Guardians. After a fierce battle between the two, Ghaul was eventually defeated. Upon his defeat, Ghaul attempts to use Radiance and is resurrected as a massive ethereal figure due to his corrupted Light, declaring himself immortal as he speaks to the Traveler directly. In doing so, the Traveler wakes from its slumber, destroying the device that was harvesting its power and then destroys Ghaul himself, sending a massive shockwave across the planet and system, restoring the Light and ending Ghaul's threat forever. With their Light restored, the Guardians succeed in reclaiming the City and drove out the Red Legion. For the first time in history, the Red Legion has known true defeat and their seemingly undefeated leader was now dead.
Despite Ghaul's death and the liberation of the Last City, the Red Legion continued to carry on the Red War but had become seriously weakened and demoralized at the loss of their leader. Even so, the Guardians continued to battle with the Red Legion across the System. The Guardians succeeded in thwarting numerous and desperate plots the Cabal planned to give them an advantage, from using Taken energy to strengthen their forces, to destroying Protheon, Modular Mind before they could utilize the Axis Mind as a weapon, and acquiring deadly weapons from Bracus Zahn and his disgraced forces.
The Legion would remain active on Mercury, following Ghaul's death, getting into a stalemate with the Vex. Another remnant of the Red Legion traveled to Mars to resupply its forces but encountered the mysterious Hive army, the Grasp of Nokris. Now the Cabal enter into a stalemate with the Hive for control of Hellas Basin while also dealing with Guardian attacks.
Return of Calus
After the death of Ghaul, the former Emperor of the Cabal, Calus, arrived in the Solar System aboard his massive craft, the Leviathan, and immediately set to work on reclaiming the empire. He gave elements of the leaderless Red Legion the chance to "join the loyalist regime," sending them on missions to collect geological data on Nessus. These transmissions are intercepted in the Adventure Invitation from the Emperor. Calus intended to convert the soil of the planet into "Royal Wine".
Calus extended an invitation to The Guardian to board his vessel for slaying Ghaul. The Guardians accepted Calus' challenge and following a long journey through Calus' palace and defeating his loyalist army, the Guardians seemingly meet Calus in person in his throne room. Facing off against the exiled Cabal Emperor, the Guardians survive his strange powers and after dealing critical damage to him, they found that the Calus they were facing was really a robotic duplicate. Regardless, the Guardians succeed in destroying the robot. Before the destruction of the machine, Calus boasted about his power and claims to know the "real truth" about the galaxy and the purpose of the Traveler. Nonetheless, he rewards the Guardians for completing his challenge and offers them a place by his side should they seek him out.
Some months later, Emperor Calus called upon the Guardians again when his Leviathan broke off a chunk of Nessus that contained a powerful Axis Mind, Argos, Planetary Core, thus clogging up the massive vessel. Instructing them to repair his ship, the Guardians travel through the bowels of the Leviathan and succeed in repairing it and battle with Argos in the fiery maw of the ship. After a perilous struggle against the Axis Mind, the Guardians succeed in disabling its shield and destroy the mind. However, with Argos's shield gone, the Guardians were soon to be devoured by the inferno of the Leviathan. Fortunately, Calus saves the Guardians and rewards them for their success and the Cabal Emperor once again offers them more than just the power of the Light, as Calus demonstrated that he can keep them safe. He also cryptically warns them that the "end" is near and therefore must be ready, as he will find them again.
Rise of Ca'uor
Some time later, following the end of the Red War, in the vacancy that was left behind by Ghaul's death, Val Ca'uor took advantage of the power vacuum and quickly asserted himself as the commander of the Red Legion. Under his direction, he hoped to resupply the Red Legion by pillaging Vex technology from Mercury and gather energy from Mars to regain their strength following the failure to capture the Traveler and defeat by the Guardians. However, both efforts led to conflict with the Vex and the newly arisen Hive faction, the Grasp of Nokris respectively.
After Xol, Will of the Thousands was killed, Val Ca'uor led a fleet against The Leviathan in order to kill Emperor Calus and seize the ship for the Red Legion's purposes. His forces occupied the Spire of Stars, inflicting many Loyalist casualties and even destroying one of Calus's robotic duplicates. However, a Guardian team was sent by Calus in response, and with the aid of his psychic powers, they raided the spire, killed many of his troops, commanders and decimated the Red Legion fleet. Ca'uor was finally intercepted at the Celestial Observatory and in the following battle, he was overpowered by the team. Calus is impressed that the Guardians have grown "fat from strength and power" and rewards them once again. Calus then tells the Guardians that he awaits the day they will stand by his side when the end comes.
A Broken Legion
Scattered Across the Sol System
Following their decimating defeat on the Leviathan and the loss of Ca'uor, any remaining survivors of the Red Legion found themselves within the Reef struggling to survive even as the region of space descended into chaos as the Fallen Scorn rampaged across the Awoken's domain. Yet at the same time, they found themselves in between the Guardian's personal war with the Scorn, losing causalities to both groups during the conflict.
In addition to their disheveled state, the Red Legion began suffering from multiple desertions such as those following Garut Gra'am who rooted themselves in Trappers Cave. The most prominent of these groups, the Unbowed Legion, made their debut in the EAZ during the Solstice of Heroes event in an attempt to take over the EAZ as a base of operations. Despite the group being led by three large Cabal commanders similar to Ghalak the Colossus, Forge Warden, they were quickly put to an end by the Guardians partaking in the event.
In response, the Cabal have made actions against deserters, even placing Wanted Bounties through the Spider, as in the case of Valus Dulurc. Against the deprivation, the legion currently faces they have been seen to continue some operations such as an attempt to take over the EAZ led by two Bond Sisters. Other operations by the Red Legion include multiple attempts to gain territory such as assaulting Lost Sectors across the system and flushing out their inhabitants. Only the Combustor Valus and Blood Cleaver would be successful in this before eventually falling to glimmer-hungry Guardians.
Opulence and Sorrow
Sometime following the Guardians' recent battles with the Kell's Scourge and dealings with the Drifter, Emperor Calus called upon the Guardians once more for a challenge that threatens his Leviathan. One of his former Shadows, Gahlran, had gone mad after using the Hive artifact the Crown of Sorrow. It was soon revealed that Calus desired a Shadow to command the Hive and further his goals but Savathûn, the Witch-Queen laid a trap for the Cabal Emperor using the Crown. Though Gahlran was bred to control the artifact to further Calus's goals, he was ultimately consumed by it, which allowed the Hive to infest the deep treasure vaults of the Leviathan.
Wanting to cleanse the infestation and have Gahlran put down before his terror brought calamity, Calus had the Guardians form a Raid team to purge his spacecraft. The Guardians traversed the treasure vaults and encounter many dangerous Hive rituals but manage to persevere and reach Galhran himself. Despite the Crown granting Gahlran great dark Hive powers, the Guardians managed to slay the Sorrow-bearer, completely purging the Hive from the Leviathan. Calus, pleased with their continued successes, rewards the Guardians with great riches and officially names them one of his Shadows.
The Guardian's accession to Shadow became sour news towards some in the Last City, particularly the Warlock Aunor Mahal, who believed that Calus is subverting the Guardians' priorities, brought her concerns and findings to the Vanguard. She proposed that the Last City should storm the Leviathan and take Calus out before his plans come to fruition. Unfortunately for the Praxic Warlock, while the Vanguard acknowledged that Calus was no ally, he kept the Red Legion in check and supplied the Guardians, nor did they wish to start a war with him. They reasoned that in time, Calus's influence over the Guardians will fall and if the Cabal Emperor does make a wrong move, they will not hesitate to send a strike team.
In the meantime, Calus extends an invitation to Eris Morn, offering her the position to replace Gahlran as Shadow of the Hive, knowing of her history with her hated enemies.
Meddling with Time
Sometime after the Guardians' conflicts with the Hive and Nightmares on Luna and defeating the Vex Offensives, Osiris calls upon the Young Wolf to Mercury. The legendary Warlock claims that after The Undying Mind's final destruction, the timeways over Mercury have been undone and worse, a council of Cabal Psion Flayers aim to take advantage of the Vex's disorganization to assume control over time itself and undo their defeat during the Red War. Their meddling with Osiris's time-altering Sundial resulted in Mercury fracturing into three different eras, each with their own timelines dictated by the Psion Flayers. The Guardians team up with Osiris to ensure the safety of time, preserve the present and save a legend, Saint-14.
The Guardians are successful in saving Saint-14 from his fate but during the three weeks of this conflict, the Guardians also manage to slay the Psion Flayer orchestrators; the sisters, Niruul, the Hollow Voice, Ozletc, the Sky Piercer and Tazaroc, the Sun Eater, one by one.
After a few more weeks of combating the Red Legion near the Sundial, the Flayer sisters would band together and use their power to fuse into Inotam, Oblivion's Triune, to finish off the Guardians. Inotam violently clashed with the Guardians for control of the Sundial but despite her vast powers and reinforcements, the Guardians are successful in slaying Inotam, ending the Psion Flayer's schemes to subvert time. Regardless of this victory, Osiris feels that other Red Legion radicals exist and the Guardians must be ready for when they will appear. Osiris would in fact be right, for unknown to the Guardians, a fourth Psion Flayer remains; Amtec, the youngest of the sisters. Having been told of the possibility of her sisters' demise, Amtec now schemes to exact vengeance upon the Guardians in the name of her sisters.
After their crippling defeat at the Sundial, a contingent of the Red Legion, headed by the last remaining Psion Flayer, Amtec, decide to direct the Almighty into an ongoing collision into the Last City itself; disabling its propulsion engines and navigation systems despite the efforts of Zavala and Ana Bray. With little to no choice, the Vanguard decide to cooperate with the Warmind Rasputin, with Guardians arming his arsenal of Warsat satellites, in order to save their home from destruction. This begins The Almighty Crisis. A minor assault was staged against the Warmind's core on Mars only to be thwarted by the Guardian and Rasputin's frames. The Legion also has forces engaging the Seraph Towers throughout the system to prevent Rasputin's armaments from destroying the Almighty.
Meanwhile, a Shadow in service of Calus made off with the Fourth Horseman, an infamous Cabal killer stolen from the Tower, to eliminate key Red Legionnaires. However, the agent was disposed of by a countermeasure put into place by Emperor Calus’s daughter, the Imperial Princess Caiatl. Regardless of this countermeasure, the Guardians were successful in reclaiming the Fourth Horsemen from a company of Red Legion soldiers guarding it.
During the past few months as Guardians succeeded in activating Rasputin's Seraph Bunkers, The Almighty had almost reached the Last City, so close, it could be seen from the Tower. Thankfully, Rasputin used his re-activated armaments and destroyed the Almighty, finally ending the Red Legion’s plot to annihilate the City, as well as destroying one of Ghaul’s most finest and destructive works. While the remains of the legendary sun destroyer plummeted into mountains close by with a small chunk chipping off a piece of the Tower, the Guardian's home was saved and the Cabal's latest scheme had been reduced to rubble. It is unknown if Amtec died on the ship or not.
With the crash site of the Almighty no longer aflame and its debris no longer falling from the sky, the Red Legion was reduced to a barren few after countless losses. Despite this, the Legion still operates. Several groups of Cabal interfered with the Guardian efforts to collect energy from Pyramid scout ships on Io, seeking to take the phantasmal energy being gathered for their own unknown uses under the leadership of many Champions. These Champions have been seen to collect blooms, concentrated amounts of phantasmal energy from pyramid scales, and secure them for extraction. It is also unknown whether or not Amtec still leads the remains of the Legion due to the possibility of her death on the Almighty remaining unconfirmed. With their current state, it is possible they could turn to either Calus' Loyalists or, more likely, Caiatl's Regime. From what is learned by the Guardians at the Tree of Silver Wings, it is extremely likely the Darkness speaks/has spoken to the Cabal.
Calling the Legion
In the wake of many destinations vanishing, Xivu Arath's Cryptoliths began corrupting many Red Legion Cabal just as Caiatl was beginning to rally the remaining remnants of the Legion through both the use of encrypted communications and blue emissaries. Caiatl commanded the Legion to return to her and to prove their loyalty by capturing Calus whilst she sent further Scouts and emissaries to the system. Entire encampments were abandoned along with mass graves reported and entire groups slaughtering each other or suffering internal conflict due to the Cryptoliths' influence leading Caiatl and her Scouts to become wary and attempt to investigate the situation. Despite many blue emissaries and Scouts sent by Caiatl, most reported the same above events.
Around the same time, Calus, the Loyalists, and the Leviathan mysteriously vanished from the orbit of Nessus. Osiris looked into its disappearance but found nothing hinting as to why the Leviathan left or where it was headed. In addition to this mystery was another. Of the Wrathborn, none being Red Legion have been encountered yet thus concerning Crow. It was later learned that the Wrathborn were not limited to the Sol System and that the Cabal empire under Caiatl had also mobilized to combat the 'disease' spreading amongst the fringes of their territory. 
Fall of Torobatl
Though Caiatl ultimately ascended the throne as Empress of the Cabal Empire following so many crippling defeats and losses to the Guardians and other factions, she remained determined to restore her people to glory. Unfortunately, Caiatl learns to her horror that her old teacher, Umun'arath, has been studying Hive rituals and had begun to worship the Hive and the power they possess. Disturbed as Umun'arath explained that she saw the future of the Cabal in the ways of the Hive and their lack of fear towards death. Caiatl reminded Umun'arath that it was she who had taught Caiatl about how the bravery to defy death was what made soldiers. Uman'arath dismissed what her former student said and now proclaimed that with the rapidly deteriorating state of the galaxy they must embrace new ways and new gods to survive. After a long silence, Caiatl came to a decision and ordered Umun'arath to step down from her council.
Some time later, Caiatl was alerted by her advisors that Umun'arath had been apprehended, in the midst of conducting what appeared to be a Hive ritual. Caiatl arrived on the scene to confront the disgraced Evocate-General and was disturbed to find her with glyphs carved into her skin and a sickly green fire burning behind her. Dismissing the guards, Caiatl demanded to know what new god her former mentor was rambling about. Umun'arath stated it was the god of war, causing the ground to begin rumbling. Caiatl declared that her obsession had turned her into a threat to Cabal society and began to pronounce her sentence, but Umun'arath then raised her hands, which glowed with energy and made the fire burn brighter while a stranger chattering began. Concerned, Caiatl drew her ceremonial blade and drove it into Umun'arath's gut, seeking to halt the ritual, but the corrupted general only laughed. Disgusted, Caiatl kicked Umun'arath off her blade and into the fire, inadvertently completing the ritual and summoning Xivu Arath, the Hive God of War, and her army to Torobatl through a massive portal.
A battle began to defend the Cabal homeworld, but the endless army of Hive ground down the Cabal's military regardless of Caiatl's efforts. The capital city was quickly overtaken by Cryptoliths which emerged throughout its streets. Caiatl herself took to the skies in her starfighter to defend her people's world, but found that while every missile she fired destroyed one set of foes, they were soon replaced, and she was eventually shot down. Wounded and with her combat suit leaking gel, Caiatl reflected on her role in the invasion, reflecting that even if she had been unwitting it was still her blade that completed the ritual Umun'arath set in motion. Xivu Arath then spoke, declaring that the Cabal had long worshipped war and thus her, and that she had finally come to claim her tribute.
With no other choice for her people to survive, Caiatl orders her people to retreat, the first time any Cabal leader had ordered. Weighing her options, Caiatl decides to venture with what is left of her people to the Sol System and recruit forces that have battled and slayed Hive Gods before: the Guardians. Aware that many of her Council will see such an offer of equal negotiation as weakness, she informs her advisors that she will demand the Guardians kneel.
The Empress Arrives
Following the Guardians managing to push back Xivu Arath's corruption and the Pyramids still encroaching on the system, the Vanguard of the Last City receives a surprise visit from the new empress of the Cabal Empire, Caiatl herself. More so that she comes peacefully and wishes to make an offer to the Guardians. Meeting with Vanguard Commander Zavala and former commander Osiris (Savathûn in disguise), Caiatl reasons that even though the Hive and the Pyramids have been pushed back, they have not been stopped and offers an alliance, bringing together the might of her empire to bear with the Guardians' Light and together, they can destroy their shared foes. In return, however, Caiatl demands that the Guardians bend the knee to her, something Zavala and the Guardians categorically refused to do. Angered, Caiatl issues a challenge to the Last City for control over the system, pitting the Guardians to face her strongest champions in a massive war game by rite of combat.
The Vanguard began using Caiatl's own embrace of ancient traditions against her, challenging the potential members of her War Council to the Rite of Proving and slaying them. Among them include, Commander Dracus, Basilius the Golem, and Val Ma'rag were slain. Gaining ground against the Empress's Chosen, Caiatl sends a private message to Zavala without the knowledge of her advisors. She told him that as a child she had believed rulers held absolute power to conquer and kill, but now understood that ruling was a form of servitude to one's people. Caiatl explained that she was beholden to the will of her people and that after the loss of Torobatl she could not retreat from the Sol System empty-handed in order to preserve their honor. Going into greater detail on her offer, Caiatl revealed that she saw the Guardians becoming the elite force of the Cabal Empire and promised that humanity would be free citizens just as the Psions now were. She asked once more for Zavala to reconsider and join the Cabal to gain revenge upon the Hive to ensure all of their survival against the Darkness. Despite the offer, Zavala and the Guardians continued on in combating Caiatl's Chosen champions in the Rites.
After several more weeks of losses to the Vanguard and tensions rising as members of both sides pushed for open war, Caiatl was contacted by Zavala, who issued a challenge for one final Rite of Proving, with each side selecting a champion and the winner setting the terms of their treaty. She agreed to the challenge and declared that if the Cabal's chosen champion emerged victorious, then Nessus would be ceded to the Cabal, humanity would support her claim to the throne of the empire, and Zavala would join her War Council as a Bracus and serve as a hostage to ensure the cooperation of humanity. However, should the Cabal lose the Rite, then she would cease all hostilities against humanity immediately and withdraw Cabal forces from Earth. Pleased by Zavala's offer, which Caiatl considered clever and a way for both sides to avoid wearing themselves out before fighting the Darkness. As she considered who to select as the Cabal's Chosen champion, she reflected that her choice had to honor tradition to hold the Cabal together. Caiatl ultimately chose Ignovun as her champion for the final rite.
With Ignovun awaiting his challengers in the heart of the Imperial Land Tank, Halphas Electus, Caiatl hoped to wear down the challenging Guardians before they reached her Chosen champion. As three Guardians stormed the tank, Zavala issued the formal challenge to Caiatl and she accepted with a wish that their shared bloodletting would lead to unity. She warned the Guardians that they would not have safe passage through the Halphas Electus, which she claimed hungered for battle and questioned if they felt the same. Encouraging them to surrender, Caiatl promised to be merciful in their shame, but Zavala accused her of provoking the conflict that they would now end. Zavala questioned why she placed warriors between their Chosen combatants and wasted their lives, and Caiatl explained that they had sworn themselves to the Rite and were free to spend their lives as they saw fit. As the Guardians approached the ritual arena, Caiatl questioned if they enjoyed the act of killing and ritual combat. Zavala told her they would do what it took to secure the peace and offered mercy. Despite a fierce battle, Ignovun fell to the Vanguard's Chosen champions and Caiatl declared that she would honor their agreement while making arrangements for a meeting to finalize the treaty.
Accompanied by Blood Guards and the Psion attendant Valir, Caiatl met with Zavala on the surface of Nessus to ritually conclude their agreement. Valir handed her a ritual blade with which she cut her palm while declaring that their blood would be the last spilt in the conflict between humanity and the Cabal Empire and the ground upon which they stood would become hallowed. She handed Valir the blade back to present it to Zavala, but as the Psion approached him the Titan's Ghost Targe was suddenly disabled by a sniper with Light-draining tech. Caiatl was shocked by this ambush, but Zavala's bodyguard Crow barely saved him as Valir attempted to slay the Commander. With Crow injured and Zavala Lightless, Caiatl charged Valir and prevented him from finishing Zavala, lifting him into the air before slamming him back into the ground and ending his life. Swearing to Zavala that she did not order his assassination, she commanded one of her Blood Guards to hunt down the sniper and bring them to her for interrogation to discover who was behind the conspiracy before watching as Crow disabled the Light-draining tech and restored Zavala's Light to him. Despite the attempted assassination, the treaty was concluded and Caiatl declared that any Cabal who maintained conflict against humanity were criminals in the eyes of the Empire and would be left to the Vanguard's justice. The other traitor, Qalec, was found and during a broadcast to her empire, Caiatl executed him, announcing the conspirators pursued their own honor rather than for the good of the empire. The empress vowed to find the remaining conspirators and deliver the same fate upon them, stating they were one Cabal and would strike only as one fist. With the armistice reached, the war between the Last City and the Cabal was officially over.
During this entire situation, the Guardians found a distress signal coming from a derelict Cabal Carrier that was once in possession of Caiatl's father, Emperor Calus, the Glykon Volatus. The Guardian discovers that the ship was originally stolen by a lone Guardian named Katabasis and his Ghost, Gilgamesh, assisted by a Psion officer under the command of Emperor Calus. The ship was used for experiments on the Scorn in the hopes that Calus would be able to understand more about the Darkness. Katabasis piloted the ship to the Reef where he rendezvous with Calus in a Loyalists vessel and it was there where Loyalists brought the Crown of Sorrow. The experimenting with the Scorn continued, utilizing the Crown as a means of observing how the Darkness interfered with the Scorn's corrupted consciousness. Many test subjects perished from "continuous neuron death" except for one who "spoke with many dead voices". This scorn would become the Locus of Communion. However, when the Black Fleet arrived, the Glykon Volatus would be caught in the very edges of this sweep of Darkness and become abandoned. Katabasis would slowly grow corrupted by the Darkness, eventually leading him to destroy his own Ghost after it began to crave its own suicide.
After boarding the vessel, learning what had happened on board, the Guardian defeats the Locus, and finds a decomposing Katabasis on the bridge, strung up with vines of the strange Darkness fauna/flora, being sucked of light by the Darkness. The Guardian would return week after week, uncovering the secrets of the Glykon Volatus and Calus's ritual with assistance from both Osiris (Savathûn) and Caiatl.
Combating Xivu Arath
After the conclusion of the brief war against the City, the lifting of the Endless Night and the appearance of Xivu Arath's forces amassing in the Reef, Caiatl's advisors repeatedly urged her to launch a full-scale invasion of the Reef, believing its still-weakened state would result in a morale-restoring decisive Cabal victory. However, out of respect for the Awoken she had heard about during her time as princess, Caital was reluctant to do harm to them. Further, on the strategic level, she considered such warmongering a distraction from their struggle against the Hive God of War, whose forces remained a persistent threat and had to be engaged wherever they emerged. Caiatl's efforts, such as personally leading a fleet ambush and boarding action against one of Xivu Arath's Tomb Carriers, occupied enough of the Hive war god's attention and vice versa that Queen Mara Sov of the Reef believed neither would risk overextending themselves by attacking the Dreaming City in force.
Nonetheless, when Caiatl learned that Savathûn, the Witch Queen, had revealed herself in the Dreaming City, she gathered her advisors and drew plans for just such an attack in order to destroy Savathûn while she was still vulnerable. In addition, intelligence from Lord Saladin (liaising on behalf of the Vanguard) and Psion agents relayed that Savathûn was a willing captive of Mara Sov, but Empress Caiatl, aware of Savathûn's reputation for cunning, schemes and lies and uncertain that Mara could outplay her, continued to weigh the decision to invade.
March on Mars
Following Savathûn's escape from the Awoken in the Reef, the red planet of Mars had mysteriously returned, albeit not the same as it once was, as the planet appeared to be afflicted by some temporal distortion. Regardless of the planet's state, Empress Caiatl mobilized the Red Legion to Mars, hoping to claim it as Cabal territory before the Vanguard could make a protest. However, as her forces were setting up fortifications, including a large battery cannon, the Witch Queen revealed herself in her massive ship, The Lure. The Red Legion engaged the Guardian in battle as they sought a means to enter the Hive vessel. Though this technically was a breach of the signed armistice between the Last City and the Cabal Empire, the Guardian nonetheless proceeded with their mission of gaining entry into the Hive ship. As they did so, they encountered a horrifying new enemy: Lightbearing Hive of the Lucent Brood. Not only them, but Savathûn herself also wielded the Light.
As the Guardian worked with Ikora in combating the Lucent Brood, they needed to hone and strengthen their Deepsight abilities to further traverse Savathûn's Throne World. This takes them to the Pyramid on Europa, where a cabal force was attempting to breach into the Pyramid and claim any Darkness-related artifacts. Eris Morn believes that the Cabal are looking for something that could provide them with the means to retaliate against "war itself", as the cabal never got over the fact that Xivu Arath effectively conquered the conqueror, destroying their homeworld. This search, however, was unsanctioned, as Caiatl never authorized the mission, denouncing the members of the search to be exiles and deserters, leaving the Guardian effectively free to engage the Cabal that got in their way without reprisal.
Following the battle against Savathûn, her Lucent Brood remained a threat, especially their Lightbearer Hive, as they had begun to conduct operations within the EDZ on Earth. However, to avoid making another conflict with the Cabal, Zavala arranged a meeting with Empress Caiatl in the Tower Hanger, where the Cabal Empress engaged in a heated argument with Lord Saladin before both the Guardian and Crow entered the meeting. Though the Guardian offered their condolences, Empress Caiatl remained angered by the breach in the armistice but Zavala was able to get all parties to focus on the real threat the Lucent Brood posed, with the Vanguard Commander stating that they need the Cabal to hit the Hive hard. Pleased with this, Empress Caiatl agreed to forgive the Guardian for those they had killed and begin an alliance with the Vanguard in combating the Lightbearing Hive. Setting up operations in the Vanguard's H.E.L.M. and agreeing to have the operation under Saladin's oversight, Caiatl gifts the Guardian a weapon made from Light-suppressing technology, the Synaptic Spear, which would allow the Guardian to sever the Lightbearer Hive's connection to the Light. Without a worm or the Light to keep it alive, the Hive would die. However, Caital explains that her Psions would use their abilities to keep the Hive in a painless state of being neither alive nor dead as they glean their minds for any intelligence on the Lucent Brood's plans.
The Guardian would begin operations in the EDZ, working alongside Caiatl's troops in finding Lightbearer Hive who have been reported to be killing Guardians and stealing their Light for some unknown purpose. With the Synaptic Spear and the Psion's Mindscape, the Guardians were able to capture a number of Lightbearer Hive and bring them to the Psisorium, where her Psions shifted through their minds. During these operations, Saladin would reach an understanding with the Cabal Empress, realizing that the Cabal also have a sense of honor.
In time, Caiatl's most trusted Psion was able to glean truth from the Hive Lieutenants: the Lucent Brood were stockpiling stolen Light within the Cosmodrome but are having trouble getting a precise location as a barrier is blocking them, hiding their activities. This forces Saladin to send in the Guardian to capture another Hive Lieutenant to further gain the intelligence they need. After gathering enough lieutenants and going through their minds, Caiatl's psion learned the true scope of the Lucent Brood's plans: they plan on storming the Moon and claiming the Scarlet Keep from Xivu Arath's forces for the purpose of conducting a ritual that would manifest Savathûn's Throne World, using the Light they had stolen from Guardians in the EDZ. In this, the Lucent Brood would be able to launch a full-scale invasion of Earth.
Gathering her fleet, Caiatl's forces surround the Scarlet Keep as the Guardian breaches in and disrupts the ritual, capturing the lead Lightbearer Wizard in the process. With their ritual ruined, the Lucent Brood's forces retreat and fall into disarray. However, despite this victory, the Vanguard's alliance with the Cabal would be threatened by the actions of Crow. Having grown increasingly unnerved with the method of how the Vanguard gained the necessary intel, Crow recklessly shuts down the machine in the Psisorum but doing so resulted in the Psion's death. Empress Caiatl learns of this and demands justice, a life for a life, but Commander Zavala was unwilling to surrender Crow's life, despite the Hunter resigning himself to their judgment. Just as Caiatl was about to kill Crow herself, Saladin Forge steps in and offers his own life in Crow's place. Commending his bravery in the face of death, Caiatl accepts Saladin's offer, his life would be forfeit but as a Bracus on her War Council for the rest of his days. Despite Crow's pleas, both Saladin and Zavala agree, saving the Vanguard-Cabal Coalition. Despite now serving as a Bracus, Caiatl allows Saladin to continue operating the Iron Banner, having grown interested in the Guardian tradition, stating that she has some ideas of her own.
In a short time, Saladin would settle in as a member of Caiatl's War Council, earning himself quite the reputation amongst the Cabal, having been challenged in a Rite of Proving six times, emerging victorious in all of them. One had him face off against a bodyguard of another War Council member, defeating him in one blow. Impressed, Empress Caiatl promotes Saladin to Valus, expressing optimism about the future the Cabal's alliance with humanity could bring. Further, at the Empress's recommendation, Saladin has even begun to organize events for the Cabal, similar to the Iron Banner, calling the contestants his "Iron War Beasts".
Despite her growing alliance with the Vanguard, a number of her forces were growing dissatisfied with Empress Caiatl's decisions and rule, leading to the Cabal Dissenters' ranks to swell and begin a propaganda campaign to gather support, undermine the Empress and coax the Cabal into joining the Black Fleet. Unable to send her own forces to deal with this act of treason, not without risking her own position, Empress Caiatl calls upon the Guardian to silence the dissenters and find out who is leading this mutiny.
Following a trail of psychic transmissions from a decommissioned bunker on Mars, the Guardian fights past the mutineers and despite the defectors putting up a resistance, they are able to destroy the broadcast transmitters before an orbital bombardment could stop them. Racing to the transmission's origin point to find out who is responsible for the messages, the Guardians encounter Qabix, Insurgent and battle with the Psion. Despite Qabix's psionic powers and reinforcements, the Guardian manages to slay Qabix, allowing them to shut down the broadcast. As they do so, Empress Caiatl finds that the broadcasts are comprised not of words but images, feelings, and impressions. Using her Optuses, Caiatl is able to see the message being transmitted, seeing a psion at the head of a full Cabal Legion. Above them hovers a black Pyramid but behind them stands a towering golden statue. A statue of her father, the former Emperor Calus, with arms outstretched and beckoning. Caiatl can hear her father's voice promising refuge and salvation which leaves the Cabal Empress unnerved. Following this, the Guardian also finds a storage vault filled with golden treasures similar to those found on Calus' Leviathan leading Zavala to believe that Calus is funding the rebellion against Caiatl. In this, Zavala agrees to have the Vanguard conduct a search for the Leviathan and Calus, and once they do, they will inform Caiatl, with the empress promising that once they do, she will deal with her father herself.
About a week later, the Vanguard discovered that Calus' forces had rebuilt their base quicker than anticipated, forcing them to travel back to the bunker and shut down the broadcasts again. Caiatl expresses that if her father is able to convince her psions to defect en masse, then their ability to wage psychic warfare will be unmatched. Despite the defectors' efforts, the Guardian is able to destroy the broadcast towers and reenter the facility. Reaching the control room, the Guardian faces off against Qabix once more and managed to defeat him before an orbital bombardment could commence. After shutting down the broadcast, Caiatl looks into the message and, this time, sees a scene of violence, along with herself, realizing that what she is seeing is the failed attempt on Commander Zavala's life, through the eyes of the assassin, and the memory of his death at Caiatl's hands. From this message, Empress Caiatl is able to deduce that only one psion would be left alive to have such intimate knowledge of the event: the traitor Yirix and her enclave.
Now knowing the identity of their foe, the Vanguard works on disrupting Yirix's operations as much as possible, leading the Guardians to attack another base sending out psion propaganda that is eroding Caiatl's legions. The Guardians enter the bunker and battle with an Insurgent Psion once more before shutting down the broadcast. In the message, Caiatl can see a group of psions conducting a religious ceremony, during a time before they were assimilated into the Cabal Empire, leading the empress to believe that Yirix is attempting to stir a sense of forgotten Psion unity, under the banners of Calus and the Black Fleet. The Empress would find this message ridiculous as the psions had long subjugated such beliefs themselves before the cabal conquered them.
The Guardian would return to storm the base after Yirix resumes to spread her messages amongst the Legions, leading tensions to run high amongst the Psions and defections to occur. With Calus's cloning operations in full swing, the loss of life is of no concern, regardless of how many times the base is taken or destroyed, as Caiatl would comment. After defeating the Insurgent Psion and shutting down the broadcast once more, Caiatl sees the latest of Yirix's messages, which shows the same message over and over again, flashing almost too quickly to perceive. However, Caiatl is able to deduce that the messages must actually be Psion divination, impressions of things yet to come. In them, Caiatl can see the Last City besieged, The Shipstealer revived, the Leviathan reborn and the Traveler itself infected with Darkness. Realizing that these are the futures their enemies seek, Caiatl reaffirms that they must remain united if they wish to forge a different path.
Unfortunately, despite Caiatl reaffirming the need for the Cabal's alliance with the Vanguard, the death of her Psion due to Crow's recklessness and appointing Lord Saladin as a member of her War Council only angered her critics further, allowing Yirix to bring more into her fold.
Return of The Leviathan
Sometime following the Vanguard-Cabal Coalition handling the Lucent Brood and Yirix's Deserters, the Guardians and Empress Caiatl would face a surprise encounter: the return of The Leviathan, the personal pleasure craft of the former Emperor of the Cabal, Caiatl's father Calus, hanging derelict near the Moon. More strangely, the Leviathan began broadcasting a call towards the Pyramid beneath the Moon's surface, causing the Nightmare phantoms to resurface and torment anyone who comes to close to the Leviathan. Believing that Calus's obsession with the Darkness has created a new threat, Eris Morn calls upon the Guardian to investigate the massive vessel.
As the Guardian ventures onto the vessel, they find it eerily deserted and large sections of it overgrown with the same dark flora that had overtaken the Glykon Volatus. Unnerved by this discovery, the Guardians venture deeper into the Leviathan but encounter a unique Nightmare that actually speaks in a voice that Zavala recognizes. However, the Guardian encounters a Loyalist Gladiator that they cannot seem to harm. Left with no choice but to hide and escape, the Guardian proceeds further through the vessel until reaching Calus's throne room, and encounters one of the Emperor's damaged robotic proxies. Investigating the robot seemed to activate it, producing the laughter of Calus himself before summoning swarms of Loyalist forces. On the verge of being overwhelmed, Eris attempts to teleport the Guardian to safety, only to discover that a power is blocking her attempts, forcing the Guardian to flee from the Leviathan on their own. Despite the Loyalists' efforts, the Guardian managed to reach their ship and return to the Vanguard to report their findings.
Eris meets with Zavala and Caiatl, explaining that the Lunar Pyramid was stirred by the Leviathan's call and it now manifests their deepest regrets, wearing familiar faces and speaking with familiar voices. Eris explains that she can bind the Nightmares, granting safe passage through the Leviathan but Caiatl balks at the thought of using Hive Magic to do so. Despite his concerns, Zavala agrees after Eris stated that the rules have been bent around them and now they must bend to survive. Though Caiatl refuses to take part in the ritual, she stands firm in leading the charge, claiming her armor is protection enough. Gathering Zavala, Crow and the Guardian to her ritual center in the H.E.L.M. where Eris had taken possession of the Crown of Sorrow, she conducts the ritual, requiring Crow and Zavala to offer their most painful regrets to the crown. Despite some difficulty, the ritual is completed, allowing Eris to create an item, the Nightmare Harvester, that draws out the Nightmares, allowing the Guardians to slay them and then imprison them within the psychic prison that Eris had made of the Crown of Sorrow. However, the ritual also forces Crow and Zavala to be actively tormented by their regrets. In Crow's case, his former life as Uldren Sov. For Zavala, he would be haunted by Safiyah, a woman he once shared a life with. Though Caiatl didn't partake in the ritual, the Empress would find herself haunted by her former co-conspirator, Dominus Ghaul.
Seeking to break the connection that Calus is attempting to create with the Lunar Pyramid, Eris has the Guardian head back to the Leviathan to take part in a ritual of severance, but for it to work, Crow must take part and face the shame and regret that his Nightmare embodies. Despite his efforts, Crow falters to the Nightmare's taunts, which manifests a powerful phantom, The Nightmare of the Fanatic, forcing the Guardian to battle it. The ritual's progression allows the Guardian to wield a new weapon, a reaper scythe, that aids them in slaying the phantom. Regardless, the ritual ultimately fails as Crow is unable to conquer his fears of becoming just like his past self. Realizing that she underestimated the ritual's complexity, Eris Morn instructs the Guardian to continue their Nightmare Containment assignments while also investigating the Leviathan.
As the Guardians patrolled the Derelict Leviathan, they encountered another one of Calus's robotic proxies which allows them to reestablish personal contact with Calus himself. Though wary, the Guardians and Crow listen to the former Emperor as he explains the condition of his vessel, the nature of the dark flora spreading, and even some personal memories involving his daughter, Caiatl.
After a time of reclusion in understanding the Nightmares, Eris returns to inform the Guardian that the best solution to defeat the Nightmares is not through denial but through acceptance. Taking another chance at the severance ritual with Crow, the Guardian repeats the process to prepare the ritual as Crow stood firm against his Nightmare's taunts. As the ritual begins, the Nightmare of the Fanatic reappears, forcing the Guardian to battle it as Crow finally accepts his past life and decides to learn from his mistakes. As Eris hoped, the ritual this time works, transforming the Nightmare of Uldren into the Memory of Uldren Sov, which causes the Pyramid's connection to the Leviathan to fray.
In time, it would be Zavala's turn to take part in the ritual, forcing him to confront his grief over the loss of his former love and the family he started with her. Despite this, Zavala refuses to speak about his past involving Safiyah, forcing Eris Morn to elaborate on the history between Zavala and Safiyah. She reveals that during Zavala's time as a student to Lord Saladin Forge, he met a surgeon who offered her medical skills to the Iron Lords. At first, the two vexed each other but over time, they grew close, enough that Zavala ultimately left being Saladin's student, married Safiyah and adopted a boy named Hakim, starting a family. Though Zavala was happy with his family, he was plagued about leaving behind his duty. Though he trained Hakim, the boy was slaughtered by a House of Devils raid, much to Zavala's and Safiyah's grief. Zavala asked for her forgiveness but Safiyah believed there was nothing to forgive. Even so, both separated and returned to the lives they once had. While Zavala would go on and become a leader amongst the rising Guardians, Safiyah would find love again and have a daughter but would ultimately pass away, leaving Zavala to continue mourning and asking for forgiveness, which he could not find.
Preparing the ritual, Zavala would help the Guardian in placing amplifiers to sever Calus's connection but would soon be tormented by Safiyah's voice before being attacked by what he believed to be Fallen from the House of Devils, which Eris believes the Nightmares are deceiving him with. At the ritual location, Zavala begins but almost immediately struggles as the Nightmare of Safiyah reminds Zavala of all he had lost and of the pain he carries with his memories. The ritual would bring forth the Nightmare of Kethiks, Grief Unforgiven, an apparition of the Fallen who had killed Zavala's son. Though the Guardian managed to defeat the Nightmare, the ritual fails just as it did with Crow, leading Eris to conclude that Zavala still carries blame and that they cannot proceed until he finds forgiveness, something that the Nightmare of Safiyah scoffs at. Admonishing Zavala for making peace with the Fallen of the House of Light, claiming that his new life dishonors his old, denouncing Zavala as a "hollowed man leading others to die" for a "silent god." Though Eris attempts to comfort Zavala stating that his true family wouldn't torment him, he remains despondent, returning to the Tower in silence. Though refusing to speak to anyone about the ritual, the Guardian is able to get Zavala to speak who admits that he was unprepared for the emotional burden that came with the ritual. He knows that Safiyah wants him to open up and confide his feelings with the Guardian but the Vanguard Commander doesn't see what good it will do.
Returning to Eris, she states that Zavala's wounds run deeper than he would allow those to see and though she understands his pain and unwillingness to open up, she likewise knows that he needs to open himself if he wishes to move beyond the past. Eris believes that if he is counseled by friends and family, there can be hope for Zavala, as there is no running from the past.
After a time, Zavala finally came to understand what he needed to do and with Eris's guidance, prepares to partake in the severance ritual once more. Despite the Nightmare of Safiyah condemning Zavala for valuing his duty and his "god" over their family, Zavala remains resolute, refusing to acknowledge the Traveler as his god. After setting up the amplifiers and reaching the ritual location, Zavala begins the severance which brings the Nightmare of Kethiks once more. Despite the Nightmare's strength, the Guardian prevails and Zavala finally manages to reach a measure of forgiveness for himself, turning the Nightmare of Safiyah into the Memory of Safiyah, completing the ritual. Though Eris commends Zavala and the Guardian, she can't help but wonder what plan Calus is planning as they severed two of his connections to the Lunar Pyramid, leaving only one, and yet the former emperor hasn't made a single move against them. She does notice however that as they remove each connection, the remaining grow stronger, which only necessitates the need to complete the last ritual for if they fail, then the Nightmares will flood from the Leviathan and spread across the system.
Over time, Caiatl tires of the situation with Calus not moving forward, and has had enough of the Nightmare of Ghaul taunting her. She misinterprets Eris' ritual as simply "conquest" of a foe and believes she is enough to take out the Nightmare of Ghaul. She advises the Guardian not to interfere, and declares an open challenge to her former Dominus, seeking battle with the Nightmare in the depths of the Derelict Leviathan. Seeing this as folly, Eris has the Guardian follow Caiatl to the ritual location. The empress, angered that the Guardians are following her, allows them to fight alongside her forces against Calus's Loyalists but forbids them from interfering with the ritual. During all of this, the Nightmare of Ghaul continues to taunt Caiatl about her supposed weakness and failures as a leader. Upon reaching the ritual site, Caiatl begins the severance but like Crow and Zavala before her, Caiatl struggles against the Nightmare who then summons the Nightmare of Dominus Ghaul, forcing the Guardian to fight it. Though the Guardian slays the Nightmare, the ritual fails with the Nightmare denouncing Caiatl as not the one he had trained when he first rose to power.
Despite this failure and Caiatl still refusing to take part in the binding ritual, Eris instead looks for a new way forward and finds a clue to one on the moon. Tasking the Guardians to investigate, they enter the K1 Revelation site on the Moon, battling with the Nightmare of Arguth, the Tormented near a relic belonging to Calus. After slaying the Nightmare, Eris had discovered a call to the Pyramid in the dying screams of the Nightmare. Eris surmises that in lieu of the severed connections to the Pyramid, Calus had used the relic within K1 Revelation as a focusing point to strengthen what remained. Now, Eris directs the Guardian to the Lunar Pyramid and there they discover Calus's Loyalists deceased, with Egregore lining their esophagus. Eris then understands that Calus forfeited their lives to ferry his mind across a great distance and hasten ingress to the Pyramid. Concluding that Calus is now desperate, that their plan is working, Eris seeks to speak with Caiatl. Speaking with the Guardian, however, Eris understood Calus knew exactly what he was doing, goading his daughter to recklessly strike out on her own. Nonetheless, with the recent discovery found near the Pyramid, Eris is able to figure out that Calus is seeking to become one with the Lunar Pyramid and claim its power. Worse, Eris believes Calus is doing this at the behest of The Witness in bringing about a second Collapse.
Finally speaking with Caiatl, Eris once again offers her support but the Empress remains hesitant as the weight of her responsibilities as leader of the Cabal makes her reluctant to engage in the situation as Caiatl herself. However, Eris states that she is not a crown but a woman with a burden and that her true nightmare is the expectations placed on her as leader. Understanding this and realizing she doesn't know what she wants for the future, Caiatl agrees to take part in the binding ritual.
After completing her part of the binding ritual, Caiatl was now prepared to take part in the severance ritual to break the last of Calus's connection to the Pyramid but Eris fears he may already made his way into the core of the Lunar Pyramid, taking note of voices she recalls from her time on Io under the Tree of Silver Wings and beneath the ice of Europa, which causes her to urge the Guardians to make haste. Returning to the Leviathan alongside Caiatl and her forces, battling against the Scorn and Calus's loyalists. As they reach the ritual site, the Nightmare of Ghaul continues to denounce Caiatl for not conquering the Last City and destroying the Guardians but Caiatl remains resolute in her beliefs. Upon reaching the site and beginning the ritual, the Nightmare of Dominus Ghaul returns, forcing the Guardians to battle it. Despite its power, the Guardians prevail with Caiatl reaffirming that she accomplished more with compromise than with conquest as Ghaul had normally done. Taking her blade, Caiatl stabs the Nightmare of Ghaul transforming it into the Memory of Ghaul, with it acknowledging her accomplishments, taking note that where he sought to conquer the Light, he burned for it but Caiatl was able to utilize it through her War Council, stating that she had surpassed him. With the ritual complete, Caiatl returns to her ship.
Returning to the Eris, she states that they have achieved their goal in severing Calus's connections to the Lunar Pyramid yet takes note that nothing on the Leviathan has changed and Calus himself has done nothing in response, making the victory seem hollow. However, Eris noticed that the Nightmares imprisoned within the Crown of Sorrow are beginning to seethe, meaning that something is coming and they are not prepared for it. Wishing to discover more before such an event were to occur, Eris delves into her research once more as she instructs the Guardians to continue with their Nightmare harvesting.
After a time, Eris would discover her worst fears realized; they were too late to sever the last of Calus's connections, as Caiatl's previous brazen attempt was the time Calus needed to complete his plan. The former emperor had extended his consciousness into the Lunar Pyramid, causing it to surge to life and begin his efforts to assume control over it. However, Eris believes there is still hope to stop Calus as not all of his power has merged with the Pyramid yet. There was still time to conduct one last, desperate, severance ritual at the seat of Calus's power to dislodge him from the Pyramid before the change becomes permanent. However, conducting a ritual of such magnitude would require the aid of Caiatl, Crow, Zavala and Eris herself altogether. Gathering the Nightmare Harvester, the Guardians invade the Leviathan, distracting the Scorn and Loyalists while the others plant their amplifiers. However, Caiatl would lose contact with the team, forcing the Guardian to head towards Calus's throne room alone as both Crow and Zavala would find themselves attacked. Reaching the throne room, the Guardian locates the hall filled with the emperor's robotic proxies and heads through a dark portal that takes them into the Lunar Pyramid itself, specifically a location called the Chantry of the Darkest Hour.
There within the Pyramid, they reunite with Caiatl who issues a challenge for her father to reveal himself as the Guardian places the Nightmare Harvester which ultimately reveals Calus in his true psionic form as a Herald of the Witness. Calus answers his daughter's call, stating his disappointment in his daughter's refusal to stand by his side and summons the Nightmares the Guardian previously faced. Despite being nearly overwhelmed by Calus's nightmares, the Guardians are able to wound Calus directly by slaying the Nightmares and even receive aid from the Memories of Uldren Sov, Safiyah and Ghaul. Despite his vast psionic powers, the use of his forces and the Nightmares, the Guardians succeed in defeating the former emperor-turned herald, ending Calus's threat.
Reuniting with Eris, Zavala and Crow, the team witnesses the memories fade away as Caiatl confirms that her father is gone, that he has given himself over to the Witness, leaving all present relieved by exhausted by what they went through. Nonetheless, the mission was a success; Calus has been pushed back, the Leviathan has gone silent and the memories have returned into the psychic noise of the Pyramid. However, while Eris commends the Guardian's efforts, she states that their battle with Calus was not a victory as they have merely bought themselves time. She further states that while Calus may be defeated, he is not gone, as he was successful in becoming a herald of the Witness and the harbinger of the Second Collapse. In addition, the Leviathan remains and it will take months to clear out the rest of the Nightmares and ensure it is no longer a threat. However, Eris remains somber as their efforts are likely for naught, for they have reached the point of no return. That the Witness is near and it is the beginning of the end.
Into Calus's Mind
As the Guardians worked in reaping the Nightmares and investigating the Leviathan's current condition, Eris Morn would find a statue of the former Emperor where the Darkness is coalesced inside but more importantly, it is connected to Calus's very consciousness. Managing to catch that connection, Eris is able to allow the Guardians to enter Calus's very mind and steal his darkest secrets but warns them that even though they are entering into a world born of Calus's thoughts, it will be no less dangerous than reality. Entering the rift, the Guardians explore the reaches of a palace-like environment but to Eris's surprise, they find the imprints of Calus's consciousness are fractured and straining. This makes it apparent that Calus is at war with himself. As they collect pieces of Calus's memories and recollections of his past, the Guardians hear echoes of the former Emperor, something that Eris believes are Calus's personal torment.
As they traverse the former Emperor's mindscape, the Guardians hear every repressed personal thought of Calus, from his rise to power, overthrowing the Praetorate, his drunken stupors to the moment Ghaul led the coup against him. As they progress, the Guardians face off against the Nightmare of Ghalran, the Sorrow-Bearer. Despite the danger, the Guardians prevail against the Nightmare and collect more memories of Calus's time during his exile before coming into contact with The Witness and vowing to become its herald and be the last being left in the universe before the end. Their journey through the expansive world of Calus's mind would ultimately have the Guardians confront a phantom of the Emperor's daughter, the Nightmare of Caiatl, Princess-Imperial. After a struggle and using the reality of Calus's mind against the Nightmare, the Guardians managed to defeat Nightmare of Caiatl before claiming the last of Calus's repressed memories. With Eris's aid, the Guardians return to their reality and from what they have gleaned from Calus's nightmares is that the former Emperor is seeking a transfiguration of sorts, believing it will help him understand the goals of the Witness. Recalling Calus mentioning the "final shape" that Eris has heard before in Hive Apocrypha and from Toland, she claims that by understanding the true goals of what the Witness seeks, they might be able to prevent a second Collapse.
While the Cabal are a militaristic species with a penchant for conquest, as evident by the existence of the Psion client race, their exact motivation for coming to the Solar System is unclear. They have a fascination with the Vex and their technology, as evidenced by their heavy presence at numerous Vex sites across Mars, such as the gate to the Black Garden and the spire that unlocks it. The Cabal also sent an expedition to Mercury to investigate a Vex structure known as Vertigo, but the members of the expedition disappeared under mysterious circumstances without a trace. It is unknown if the Cabal have attempted to visit any other worlds apart from Mercury, Mars, Io and Nessus.
When a Cabal army goes to war it is exiled from the Empire, and is not permitted to return unless victory is secured. This presumably provides Cabal troops with the incentive and motivation needed to endure long-term campaigns, though they can still wear down eventually. Those on Mars showed signs of exhaustion as they were forced to fend off endless Vex assaults in addition to devastating Guardian strikes.
Given the numerous casualties suffered at the hands of the Guardians, the Cabal have set their sights on the City, looking to find ways of neutralizing their self-resurrection abilities before committing to war. Psion Flayers have been indicated to have already analyzed certain areas where Guardians cannot self-resurrect, such as the vicinity of the Black Garden, and that the Hive on the Dreadnaught possess the means of extending these areas. They are capable of very extreme tactics in the name of the Empire; from blowing up entire planets for being in the way, to blowing up most of the system. Cayde-6 considers the Cabal to be war criminals for their brutality. Yet, for all their ferocity, it has been noted that the Cabal seem to secretly be running away from something terrifyingly powerful - possibly the Darkness. The Cabal, under the Red Legion, finally managed to find a way to disable Guardians' self-resurrection abilities through the Traveler Cage but it was later destroyed by the Traveler.
The Cabal's primary reason for coming to Mars was apparently to mine its resources and investigate human technology. This changed with the discovery of the Virgo Prohibition and later the Guardians. Even when the Red Legion arrived, the Cabal still displayed an interest in mining. Much of the Cabal's ambitions also centered around one of their core cultures, the Rite of Proving and the Bell of Conquests.
The Cabal are a bipedal, hulking species that appear to be carnivorous, as evidenced by their many sharp, irregular teeth. They have wrinkled, leathery tan-grey skin, a tall skull, dark wide-set eyes with slit pupils, and a very high, inverted-V-shaped upper lip that exposes the Cabal's upper gums and fangs. They come from a warm, humid climate, so they have to be constantly hydrated within their suits. Therefore, while a resilient species, Cabal cannot survive in Mars's blistering environment without climate-controlled gel suits. Cabal have long lifespans, in one case having lived well over a thousand years without any apparent infirmity.
The Cabal species has male and female sexes, and presumably reproduces sexually. The Cabal have advanced cloning and genetic manipulation technology, as exemplified by the Ceremonial Bathers spawned by the Leviathan's cloning facilities. 
References in the Grimoire indicate that the Cabal have females serving in their rank and file. However, they are indistinguishable from the males in gameplay, making the Cabal seem androgynous in human eyes. Depictions of two known female Cabal, Caiatl and Umun'arath, suggest that they have tusks, while males do not. Recordings from the Councillor Match suggest that young female Cabal get 'first tusks', perhaps implying that these can be shed like the antlers on a deer. This is supported by certain unique Cabal enemies such as the European Aerial Zone Bond Sisters, who lack tusks but are confirmed to be female.
The Drifter claims that Cabal do not have any fat on their bodies, only muscle.
The Cabal language is Ulurant. It has been described as "grunting" and "moronic", lacking in subtlety.  Nevertheless, the City has yet to fully translate it or its various dialects.  The Cabal are confused by the term "Ghost", translating it as "Dead Person",  though this may be a simple error in semantics as the word "ghost" indeed exists in the Cabal vocabulary.  They do not appear to have a word for "hubris"  or "retreat" ; conversely, they have six words for "advance". In the Warmind comic, it is written using a heavily distorted English alphabet, with each word flipped upside down and reversed. When speaking to Uldren Sov in the Black Garden, a legionary's speech is transcribed with the tone of a stereotypical London accent.
Like humans, Cabal make use of the decimal or base-ten numeral system. A system similar to Roman numerals also appears to be in use, primarily seen in the naming of heavy vehicles such as the Cerberus Vae III or the Dantalion Exodus VI.
Research and development
The Cabal are always looking for ways to increase their power, and have devoted a lot of time to finding and adapting the technology of other races. However, they frequently do not fully develop the technologies they use, leaving structural weaknesses to be exploited, as Ikora notes in Reversing the Polarity. Ghost also noted on Mars that their security systems are absurdly easy to exploit, claiming they were less complex than DOS, which is a family of basic operating systems that were antiquated even before the human Golden Age. A poor imitation of a Vex device was also found in the Cabal base on Io. They also frequently tamper with forces they hardly understand, whether it's the Traveler's Light, the Taken's radiation, or the Darkness itself.
The Cabal in the Solar System are but one arm of a vast interstellar Empire, and in the words of Valus Tlu'urn are "a few scout legions bogged down in attrition war". The nature of the upper echelons of Cabal leadership, including the identity of the leader of the Cabal in the Solar System, is unknown, except for the fact that the Cabal as a whole were ruled by Dominus Ghaul, who has final authority over military decisions, before Caiatl took over as Empress, following the death of Ghaul and the evacuation of Torobatl. The Praetorate is an influential military aristocracy that controlled the Empire's Legions in the past, but holds somewhat less power under the reign of Ghaul.
Various military ranks appear among the identified Cabal leaders:
Titles such as Emperor and Consul are used by the Empire's political leaders. Calus held the title of Emperor before his exile. However, upon conquering the Empire, Dominus Ghaul refused to claim the title after he overthrew Calus, insisting that there would be no more Emperors, though his supporters sometimes refer to him as "the Emperor" anyway out of respect. The Imperial crown would later be restored by Caiatl, daughter of Calus and former protégé of Ghaul.
Bond Brothers is another title and designation given to Cabal Commanders who work in tandem and display a unique sense of Comradery.
The Legions themselves are organized into smaller sub-units:
Some Cohorts may have Auxiliary units attached, such as a noncombatant Strategic Intelligence Maniple.
The Red Legion appears to use an alternate command structure with eccentric designations: it is divided into Fractures, which are further subdivided into Scales, Bridges, and Masses. Companies have also been identified, though how they fit into the previous is unclear. 
The Cabal seem to be great architects, they build massive structures and build them within a short period of time depending on the legion. The Red Legion built Firebase Hades in a short period of time without being detected, but this fast building might explain the weaknesses within the Cabal structures, which can be exploited. Most of them are impressive but sloppy in build, easy to breach, and are able to be shut down or disabled for long periods of time (e.g. Firebase Hades, which is currently disabled).
Named individuals and mini-bosses
Cabal Empire leadership
Solar System leadership
In addition to the Cabal themselves, the Cabal Empire includes numerous other species whose civilizations were incorporated into the Empire as clients, either willingly or by force. Several of these were part of the Empire before Calus was ousted during the Midnight Coup, while others were encountered by Calus during his exile and joined his Loyalists faction.
The Cabal rely upon a thick, black, oil-like substance to fuel and supplement much of their technology. It is composed of many unidentified chemicals and is potentially toxic to non-Cabal. They possess technology, or potentially individuals which enable them to shape and transform the features of planetoids, much like the Hive, but not on the level of the Traveler. This technology has been used by them to draw Mars's moon, Phobos, very close to the planet. They are capable of engineering on enormous scales, as demonstrated by the Traveler Cage, the Almighty, and the Leviathan, and routinely destroy planets for fuel or simply for "getting in the way."  Through the Traveler Cage, they demonstrate the ability to manipulate Light via technological means, and can even forcibly bestow it on beings not originally blessed by the Traveler.
List of appearances