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In the aftermath of the Red War, the Legion would fracture into various leaderships such as Val Ca'uor, Valus Thuun, The Psion Flayer Sisters and also see the return of Emperor Calus, their former emperor who aims to recruit them into his Loyalist regime along with his daughter, Caiatl, the Princess-Imperial who seeks to see the Legion rise and march once more.
The Ghost Primus
Emperor Calus impressed by a young gladiator Ghaul, would appoint him to Primus of the Red Legion to better use his talents. Due to his albinism, Ghaul quickly became known as the Ghost Primus. Ghaul quickly became indispensable to the Emperor not only for his skill in battle but also his wisdom. Ghaul soon found himself as the right hand of Calus, who would often discuss his plans and ideas with Ghaul to refine them and temper the Emperor's passion with discipline.
As his command over the Red Legion grew, the Legion became more loyal to Ghaul over their emperor. This growing support enabled Ghaul to launch a successful coup against Emperor Calus, with the Red Legion accompanying him to arrest Calus and sending him and his supporters into exile inside The Leviathan.
A New Empire
With the Red Legion in control of The Cabal Empire, Ghaul titled himself Dominus and declared himself the leader of a new Cabal regime where there would be no more emperors and where everyone could attain greatness if they worked hard for it. Under his direction, the Cabal militarized and became a conquering, expansionist empire, and the Praetorate regained little of the power it had held before Calus, although the Consul remained Ghaul's advisor. Ghaul eliminated much of the decadence of the Empire in favor of perfecting the Cabal into what he viewed as an ideal war-driven form. Knowing that Calus remained alive and a potential threat to his rule, Ghaul took steps to hide his movements from the exiled Emperor in an effort to keep his plans secret.
Likewise, the Red Legion during the Empire's complete reconstruction became a Naval powerhouse. Under Ghaul and Umun'arath's command, the entire Cabal naval doctrine, predominantly that of the Red Legion's shifted to an adaptive, dispensable, and swarm tactic stratagem. Cruisers described as "beautiful deterrents of Calus' armada" had been stripped down near completely into "hasty and crude" Frigates and Carriers. These new Cabal warships were made to be expendable, quickly produced, and used in unison, specifically in brutal broadside exchanges with Hive Spacecraft. War Fleets now suckled fuel from enormous carriers and operated as groups instead of the "proud, independent" cruisers of Calus' old Empire. Much of this extreme shift of doctrine was pushed by the rim wars of the Cabal against the Hive which, as described by Councilor Match "leave no time or space for elegant vector dances" when facing the Hive's innate slip-space abilities. Despite this doctrine being best suited against Hive, the Red Legion stuck by it as their key naval principle and seemed to never greatly change it.
It should be noted, however, that either a few of Calus' cruisers presumably survived conversion and had been utterly retrofitted into grand Capital ships, or the Red Legion made some exceptions and constructed much larger battlecruisers that served as juggernauts for orbital bombardment and stuck out like sore thumbs amongst the new Cabal Fleets. One such example of these Capital ships is the Retribution.
The conversion of the Empire was not just limited to discarding decadence and the old naval doctrines. Conversion of the Empire to Ghaul and the Red Legion's new regime spread to the Athenaeum Worlds. Formerly sites where citizens, primarily artisans and thinkers, would travel to be inspired from "alien wonders from across and beyond the Cabal." These worlds were shut and closed off in the Legion and Ghaul's reign. Worlds of the Cabal Empire were radically transformed. Wondrous inventions of old became replaced by grim weaponry and militant architecture. Great gardens and flora of the Cabal's worlds were removed to pave way for industrial expanse. Almost all of the properties that Calus had instilled were being dissolved. Emperors to Domini. Opulence to martial grit. Cruisers to swarms of frigates. Gardens to factories.
In some of the Legion's earliest campaign's under Ghaul, the Dominus had employed the use of Psions amongst the Legion to mask his fleets from the Hive in his conquest of their War moons on the fringe of Cabal space to ensure a "buffer" against invasion.
One of the better documented and most important of the Red Legion's campaigns involved one of the Empire's client species, the Clipse. Living amongst a harsh and xenocidal environment, the Clipse had been brutally forced to change, very similar to the conversion experienced by the Cabal, to a martial and war-driven race. Seeking security in the fallout of the Midnight Coup, Ghaul sent a fleet of Red Legion towards the Clipse homeworld in order to secure their loyalty and "win" the centuries old conflict that had long tormented the toiling Clipse. The contingent of Red Legion in their occupation and assistance of the Clipse quickly discovered, however, that the only way the harsh ecosystem would involve taking the planet with it. Attempts at utterly terraforming and transforming the Planet's climate were all botched and only poisoned the world and Clipse further. Shock attacks and "clear and hold" tactics repeated again and again proved futile as even though the Red Legion and Clipse could fend off the threat - they could not stop or reverse it. Despite a century's worth of effort expended by the Red Legion, the operation was considered "no longer essential to the strategic security of the empire" by Ghaul and the Red Legion contingent abandoned the Clipse. The Clipse would remain loyal to Ghaul to the bitter end, trying to earn his favor back by attempting to best Calus and the Leviathan when they appeared. Although many Clipse would eventually be taken into arcologies, their homeworld would be obliterated by its moon, Kaga-Clipse's guns.
Sometime following the conversion of the Empire, Ghaul and the Red Legion had constructed a titanic vessel comparable to a moon in length and utter size. This vessel , which would become known as The Almighty, became the centerpiece of all Cabal Fleet's along with the crown jewel of the Red Legion. It was seen as an immense engineering feat to the Cabal and held to an almost zealous or holy stature. The loss of the Almighty would be as impactful if not more impactful than the loss of Ghaul.
the Red Legion would go on to conquer hundreds of worlds at Ghaul's orders, deploying The Almighty against those who refused to surrender. Though the vast majority of these wars and campaigns are undocumented, it is known one such assault occurred as close as the Trappist system. In most of these campaigns the Red Legion sought any and all information on the Traveler.. They were said to have never once failed.
Many celebrations and ceremonies of countless victories were held by the Red Legion. One such ceremony would be interrupted by Rull and his assassination of Iska'al and Moli Imoli with Rull perishing before Ghaul just as he had killed the Everjoy. In the days immediately before the Red Legion set out to the Solar System to wipe out the Guardians, Calus deployed his Shadows to assassinate the various conspirators behind the coup that deposed him. While the Shadows succeeded in eliminating nearly everyone on Calus's hit list except Caiatl, Umun'arath, Otzot (additionally referenced during Insight terminus strike), The Consul and Dominus Ghaul, none of them survived their mission. Although they succeeded in infiltrating Ghaul's vessel, the Shadows perished one-by-one against overwhelming odds. Nohr slaughtered three-hundred of Ghaul's best warriors with her bladed shield before facing off against the Dominus himself. She was the last Shadow standing, and Ghaul killed her, much to the grief of Calus.
Preluding the Red war, it was discovered that, with the assistance of the Skyburners, the Red Legion had figured out how to drain the paracasual properties of the Traveler after rugged research and intel taken from the Hive Dreadnaught. With this information combined with the years Ghaul had already studied of it and "the worlds it had touched", the Red Legion was able to fulfill its goals and construct a cage device that could extract the Light from the Traveler and bestow it upon others.  This valuable information, along with the schematics to the Cage would be stored onboard the Almighty.
The Red War
Upon receiving a distress call from the Skyburners, the Legion prepared an attack against the Last City on Earth. Psion Operatives managed to compromise the cities outer sensors, defenses, and outposts to conceal their presence. Using this to their advantage, they launched a successful invasion on the Last City while attacking other places like the Reef. The Legion would cripple the Last City and devastate the Guardians by using the Traveler Cage to suppress the Traveler's light. In attacking the City, Ghaul sought to show the Traveler the error of its ways in choosing humanity over the Cabal and establish a new order of Cabal Guardians from within the ranks of his own species.
Following the attack, the Red Legion began to quickly spread everywhere in the Solar System. On Nessus the legion attempt to excavate ancient Vex ruins and unearth the ancient Vex Mind Protheon, Modular Mind to capture. On Io, they attempted to drain Io of its abnormal Light which accidentally summoned the Taken, forcing them to leave their many dig sites. On Mars the remaining Legions gathered at Meridian Bay for one final assault and the Red Legion led the charge. The stalemate was broken, the Vex Virgo Prohibition was destroyed, Bastion retaken, and the Gate to the Black Garden was disabled, even on Venus. On Mercury the now-Lightless Titan Sunbreakers were destroyed.
With their security being lax, and Ghaul being preoccupied by wanting to understand the Traveler, their greatest weapon, The Almighty, was disabled by a Guardian. This led to a full on attack on the Red Legion-occupied City by more Guardians, spearheaded by the Vanguard. With pressure mounting and his temper boiling over, Ghaul murdered the Consul, who criticized his obsession, and went to take the Light to become a Lightbearer himself. For a short while he fought the Guardian, Ghaul ascended into a massive figure of pure Light just as the Traveler awoke, who smited the Dominus once and for all. Even in it’s aftermath, Red Legion weapons are used in Shaxx’s Crucible to help train new Guardians.
Ghaul's death and the Legion's defeat at the City did not substantially hinder their war machine.
Following the events of the Red War, leadership began to fracture with the death of Ghaul and a number of senior Primus and Valus personnal having been hunted and killed by Guardians in the ensuing aftermath. The line of succession eventually fell to Val Ca'uor, who quickly established himself as the new leader of the Red Legion. Rather than return to Torobatl in disgrace, the newly appointed leader arranged to have the Legion's arsenal restocked and their strength rebuilt. To capitalize on the limited Guardian presence at the time, Ca'uor deployed Red Legion forces to Mercury to harness Vex technology and Mars to siphon ample energy.
In hopes to find a reality where they won the Red War, Valus Thuun lead an invasion of survivors from the Almighty into the vast alternate realities of the Infinite Forest on Mercury. Coming close to the map of the Forest, Thuun and his forces would become trapped in an endless combat loop by the Vex and killed by Guardians on repeat. 
On Nessus, Red Legion forces lead by Kargen, the Technocrat launched an incursion into the Insight Terminus, a Vex installation of great interest to the Psion Flayer. Kargen's attempt to steal Vex data with an OXA Machine prototype would only be thwarted by a Guardian fireteam that killed the Psion in cold blood.
At the Hellas Basin on Mars, the Red Legion under Val Palusk instigated a raid on BrayTech Futurescape to steal power from the facility. Their efforts would only incure the Guardians to strike back with an ambush to kill Palusk and disrupt their supply chain.  Meanwhile, a group of Psions would make a failed attempt to evolve into Flayers by stealing power from Rasputin's nodes, to which their efforts were thwarted by Guardians as well. 
Faced with countless setbacks by the Guardians, Ca'uor would lead the Red Legion in a final push aimed to commandeer The Leviathan from Calus, to whom he loathed for being envious of Ghaul. Ca'uor launched a massive Red Legion fleet against the Emperor and his Loyalists, where his forces pushed into the Spire of Stars at the top of the Leviathan itself.
Following Val Ca'uor's invasion, Emperor Calus ordered an unsanctioned Guardian Raid team to repel the Red Legion, offering further riches and rewards upon their success. The Guardians heeded the exiled emperor's call and ascended the Leviathan's spire, just as the acting commander destroyed one of Calus's robotic proxies. Upon confronting Ca'uor, the Guardians engaged the Red Legion's elite forces to prevent them from taking control of the Leviathan. Using the Leviathan's own formidable weapons, the Guardians managed to decimate the Red Legion fleet blockading the Spire and killed the Val in a climatic battle. In the wake of losing the majority of their fleet, their ground forces and leader, the Red Legion was forced to withdrawal in disgrace. Ca'uor's death would officially mark the effective end of the Red War.
A Scattered Legion
However, this was not the end of the Red Legion, the Guardians started attacking the Legion more and more aggressively, instigating a skirmish with the House of Dusk Fallen, shutting down their anti-air defenses at Firebase Hades, allowing air bombing runs and raids to take place on the facility, directing the Taken assault on the EDZ toward the Legion, taking their fuel and supplies, and with the discovery of lost sectors, their leaders to came out of hiding, allowing multiple assassinations to take place. On Nessus, their commander in The Conflux, Primus Cal'aug, was killed by The Young Wolf, stopping the Legion from undergoing any further operations on Nessus. On top of that, Firebase Hades was disabled, most of their supplies were stolen and they had to deal with heavy losses due to failed offensives against the City and The Fallen.
Meanwhile on Mars, things were supposedly going well for the Legion and was a sign the Legion was still a major force with it being the only place the Legion still had power over. However, with the polar ice caps melting after satellite impacts from orbit, a new threat emerged, The Grasp Of Nokris, and with that the Red Legion saw their progress on Mars quickly being undone in Hellas Basin as they fought a war with an enemy they didn't understand. It is unknown if they fought with the Grasp of Nokris all over Mars or if it was isolated to Hellas Basin.
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.
Meddling with Time
More recently a family group of Psion Flayers, having commandeered Osiris' time-traveling Sundial, split Mercury into three alternate timelines that threaten to span beyond the planet and into the system. It is their intention to undo Ghaul's defeat, or, failing that, gather enough Light from the future to buy their way back into Calus' favor. Though the Psion Flayer sisters, Niruul, the Hollow Voice, Ozletc, the Sky Piercer and Tazaroc, the Sun Eater, managed to create a border realm for themselves, the Guardians would ruin their plans. One by one, the Psion sisters would face the Guardians and be defeated. After weeks of their forces being eliminated, the three sisters, driven to desperation, used their vast psionic powers to merge into a single being, Inotam, Oblivion's Triune. Despite Inotam's vast powers, the Guardians would nonetheless prevail against her, thwarting the sisters efforts to subvert time. However, one sister remains, Amtec, who was informed by her sisters of their possible demise and now schemes to avenge them.
After their crippling defeat at the Sundial, the Red Legion, headed by the escaped Psion Flayer, Amtec, decide to use the Almighty to crash into the Last City itself. With little to no choice, the Vanguard decide to cooperate with the Warmind Rasputin, with Guardians arming his arsenal, in order to save their home from destruction. This would kickstart The Almighty Crisis..
Despite Amtec's efforts, however, the Almighty was destroyed by Rasputin, with the help of the Guardians, before it could collide with Earth, resulting in Amtec's plot ending in a total failure for the Red Legion. Amtec's final fate is unknown, but she was possibly onboard when the Almighty was annihilated and perished in the explosion.
With the Almighty's crash site no longer in flame and its debris no longer falling from the sky, the Red Legion were reduced to a barren few after countless losses. Despite this, the Legion still operates. Several groups of Cabal interfere with the Contact public event in hopes of harnessing the phantasmal energy seen utilised in many Champions brought to the forefront. It is unknown if the Red Legion in their desperation have managed to use the energy to create Champions, or if the champions are derived from another way. It is also unknown whether or not Amtec still leads the remains of the Legion due to her possible death on the Almighty unconfirmed.
Despite the huge loss surmounted over the years, including losing the Almighty, remains of the Legion still operate. Several groups of Cabal are seen interfering with the Guardians Contact events of Io to secure motes and blooms with Champions seen securing blooms for extraction. As for their current fate, the remaining Cabal in the system will either turn to Calus’ Loyalists or to Caiatl, the Princess-Imperial’s regime, with the latter seeking to raise the Legion once more.
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.
In addition to this mystery was another. Of the Wrathborn, none being Red Legion have been encountered yet thus concerning Crow. With the impending threat of the Pyramids, several Red Legion Blood Guards meet with the former and current Commanders of the Vanguard; Osiris and Zavala, to discuss the situation at hand.
Red Legion troops can be primarily identified by their signature gunmetal and red color scheme, with some troops having gold, silver, or orange highlights depending upon their rank. They are also more heavily armored than other Cabal Legions, wearing metal plates over a bodysuit of War Beast scales.  The command structure and tactics of the Red Legion are more aggressive and agile than any Cabal Legion observed before, with deadlier weapons, advanced technology, and battle techniques. The Red Legion also has a handful of new units that operate in the field. Majors will typically wear silver armor, whereas Ultras wear gold armor.
List of appearances