The Vex are a collective intelligence of time-traveling cybernetic  war-machines. They have been encountered on several planets, moons and other celestial bodies in the Sol system, among them Venus, where they have built the Citadel and the Vault of Glass, and Mars, where they guard an entrance portal to the mysterious Black Garden. Additionally, they have laid claim to Mercury and Nessus, both of which have been fully converted into Machine Worlds,  and have established a foothold in Echo Mesa on Io. Lately, the Vex have made a resurgence upon Luna, seeking to claim it from the Hive.
The Vex have been described as a "hyperintelligent time-spanning thought-mesh", a collective mind composed of countless component intelligences distributed across time and space. The mobile Vex machines encountered by Guardians are merely containers for these intelligences, which carry mind cores filled with milky radiolarian fluid - hypothesized to be the only remnant of their distant biological origin.
Vex come in a diverse array of shapes and sizes, but the majority share features such as triangular or conical "heads," single glowing photoreceptors, jointed limbs, and in several cases arrays of flexible tentacles. Despite their often animalistic appearance, the Vex appear to be mass-produced units, constructed of an unknown metal alloy resembling hammered brass. Headshots on humanoid Vex do not do much damage and instead send them into a berserk state; however, shooting the exposed mind cores in their abdomen will cause them to explode. The Vex travel to the Floating Gardens to recycle their mechanical bodies when they are no longer functional.
According to the Lore Book "Unveiling", in the state before time and the universe began, the Light and Darkness engaged each other in a "game", analogous to a massively more complex version of the "Game of Life" invented by Earth mathematician John Conway; in the Book, this game is described allegorically as being played using flowers in a garden. This game would always end in one outcome: a self-perpetuating pattern which subsumed all others in the game. While this pleased the Darkness, the Light became "vexed" by this result.
When the Light and Darkness began to fight with one another in the primordial state of reality, the final patterns which had dominated their previous "games" escaped into the nascent universe. The patterns manifested themselves within matter, influencing the chemistry within the cores of comets orbiting young stars. These comets then rained down on lifeless planets, and the molecules they carried developed into the first radiolaria. From this point forward, the Vex were driven to once more totally dominate the reality they found themselves in, though operating on "outdated" rules that did not account for the acausal powers of the Darkness or the Light.
The Ancient Past
The earliest historical event associated with the Vex is when the Hive god Crota, Son of Oryx opened a portal to a place where the Vex were present, hoping to find a secret power for himself. Instead, he allowed the Vex to invade Oryx, the Taken King's throne world, the High War. At first unsuited to the Ascendant Realm and the rules governing its reality, the Vex quickly learned of the Hive's Sword-Logic, creating Quria, Blade Transform to investigate it. Through Quria, the Vex learned to achieve divinity by killing all who opposed them and adopting worship as a primary function. Though Oryx eventually succeeded in eliminating the Vex from his realm, they preserved what they learned and passed it on to the rest of the Vex hive mind. Quria would later ambush Oryx when he attacked the Nicha Thought-ship. In the ensuing battle, Quria generated a simulation of Oryx's original form: Aurash. As Oryx was distracted by the simulation, Quria devoted the rest of its resources to sending what it had learned to the rest of the Vex hive mind. Quria was then Taken and given to his sister, Savathûn as a gift, however, Oryx allowed Quria to retain a portion of its own will.
The Golden Age
During humanity's Golden Age, Vex structures were found on Venus dating back to a few billion years before humanity's existence. Ishtar researchers suspected that the Vex ruins came from an alternate Venus and came into being when the Traveler transformed Venus into a habitable world.
The Collective also recovered a live specimen of Vex and discovered that it had created an internal simulation of themselves, accurately predicting their every move. To Collective researchers, this ability raised profound philosophical quandaries about the nature of reality. Eventually the researchers were driven nearly to madness, as they started to wonder if they themselves were just Vex simulations, so they decided to bring in a Warmind to intervene on their behalf. Warminds were many orders of magnitude more complex than humans, and it was believed that the Vex would be unable to simulate them; thus, the Warmind's presence and actions would be a sufficiently chaotic variable to allow the researchers to discern which universe was real and disrupt the simulation.
The Vex first appeared on Mercury during the Golden Age as well, shortly after the Traveler terraformed the planet into a garden world. Dendron, Root Mind was created following the Vex's arrival, and began converting the planet into a Machine World that would house the "reality engine" known as the Infinite Forest within its core.
During or before the Collapse, the colony ship Exodus Black left Earth on a trajectory out of the solar system. It was intercepted, however, by the planetoid known as Nessus, which had become fully converted into a Vex Machine World and had left its usual orbital patterns. The entire crew of the Exodus Black was captured or killed, with some being kept alive by the Vex for a time for experimentation and analysis.
The City Age and the Taken War
When the Guardians Kabr, the Legionless, Pahanin, and Praedyth ventured into the Vault of Glass on Venus, a major confluence of the Vex network, they were thwarted by the Templar and its Gorgons. Pahanin managed to escape, but Kabr became assimilated and Praedyth was trapped and lost to time. The Guardians, seeking to further break the Vex's power in the wake of the Black Garden Heart's destruction and avenge Kabr's team, formed a new raid team to breach the Vault of Glass. After a dangerous struggle, the Guardians manage to breach the Templar's indestructible shield and destroy the Mind. Further, the Guardians evade the Gorgon's abilities and bypass their labyrinth, proceeding to the core of the Vault. At the center of the Vault, the Guardians face off against Atheon, Time's Conflux, the Vault's overseer. Battling the powerful Axis Mind across the time-ways, the Guardians succeed in destroying Atheon, dealing a critical blow to the Vex.
Praedyth himself was forgotten until the time of the Taken War, when the Taken began to blight the Vex network. After receiving a distress signal from Praedyth, The Guardian was sent to the Vault to investigate and was unexpectedly granted access by the Vex. Inside, the Guardian discovered a series of Dead Ghosts Praedyth had left behind. Praedyth revealed through recordings within the Ghosts that he had seen what the Vex had calculated would be their future: eons hence, they would be completely corrupted by the Taken, becoming an eternal part of the legacy of Oryx, the Taken King. Although the Vex were able to foresee this future and compelled to seek a way to avert it, they concluded that this grim fate was inevitable without the Light; allowing the Guardian to fight the Taken blight that plagued them was an act of desperation. Traveling through a portal, the Guardian was transported to the Vex's future, where the blight was defeated, the Vex were spared from their fate, and Praedyth's remains and Ghost were recovered. Despite this moment of cooperation, however, the Vex still had no intention of returning the favor or sparing the Last City.
On Mars, the Vex (under the Virgo Prohibition) waged an intense war with the Cabal, who managed to repel the machines despite the vast numbers of them that continually assaulted Cabal positions. The reason for this massive, if ineffective, offensive against the Cabal is that the Vex were surging to protect the Black Garden, which the Vex are being summoned to for an unknown purpose. Guardians who succeeded in breaking into the Black Garden discovered that the Vex in fact worshiped an entity within the Garden known as the Black Heart, an aspect of the Darkness that had lent power to the Vex. Even after the destruction of the Sol Progeny and the Black Heart, the Vex sought to control the Black Garden and pull it back out of space and time. Besides the Black Heart, the Vex may have another connection with the Darkness; Osiris speculated that Vex structures such as the Timekeeper are designed to activate in the presence of the Darkness.
In recent times, the Vex had suffered numerous setbacks across the system - a large number of Vex Axis Minds were destroyed by Guardians, leaving the Vex network in disarray. With the arrival of the Taken, attacks against the Vex had only escalated. The Vex have yet to counter these failures, though some believe the cybernetic machines have begun preparing countermeasures as Variks, the Loyal notes, following Skolas' defeat, "Old machines are waking up...".
The Red War
By the time of the Red War, two years after the Taken War, the Vex had come under attack by the Fallen House of Dusk and the Cabal Red Legion on Io, Mercury, Mars, and Nessus. Of note, on Mars the Red Legion quickly succeeded against the Vex where other Cabal legions had failed for decades: they destroyed the gate to the Black Garden and drove the Vex out of Meridian Bay. According to Cayde-6, the Red Legion has brought even more of their might to bear on Mars than on Earth. With the gate to the Black Garden having been destroyed by the Red Legion, it is unknown if the Vex still have the means to access the Garden itself. It's possible the entrance from the Tharsis Junction still exists and the Garden is still accessible.
On Nessus, the Red Legion had begun drilling into The Inverted Spire, hoping to study and utilize Protheon, Modular Mind as a weapon but the Vex responded violently, causing a warzone to break out near the drilling sites. The Vanguard found out about the legion's efforts and sent in Guardians to destroy Protheon before the Red Legion could capture the Vex Mind. After fighting through Vex and Cabal forces, the Guardians descended into the Inverted Spire and faced off against the Vex entity. Despite its firepower and altering the battlefield, the Guardians succeeded in destroying Protheon, depriving the Vex of an Axis Mind and the Cabal of a potential new weapon.
While on Io, the Vanguard pin-pointed the Vex's machine conversion of the moon at The Pyramidion, lead by Brakion, Genesis Mind. Not only do the Vanguard want to put a stop to the Vex's plans to turn Io into another machine world but also prevent any lingering Taken from corrupting the Genesis Mind into a powerful Taken entity. Storming the Pyramidion, the Guardians, guided by Asher Mir, evade Vex traps, Vex defenders and Taken enemies and enter a pit that leads to the Genesis Mind. Battling the Vex Mind, the Guardians succeed in destroying Brakion, hindering the Vex's efforts to convert Io and granting Asher Mir as sense of vengeance as it was Brakion who nearly converted him into a Vex machine.
Curse of Osiris
Following the death of Dominus Ghaul and the reawakening of the Traveler, Vex Minds began to call the modern Vex, Precursors, and Descendants to Mercury, in order to bring forth a dark future in which only they dominate all life and both Light and Darkness no longer exist, through the means of the Infinite Forest. This required the Vanguard to locate Osiris, in the hopes of stopping them. Despite her reservations, Ikora Rey, the former student of Osiris, gives her blessing to the mission and gains assistance from the Cult of Osiris.
Though the Vanguard gained an ally in the exiled warlock's Ghost, Sagira, the Guardians traveled across the Infinite Forest to find Osiris while also thwarting the Vex's plans. After encountering reflections of Osiris, the Guardians face the mastermind and instigator of the Vex's plans, Panoptes, Infinite Mind, an extremely powerful Axis Mind with the power to delete the Vex's enemies within the Forest. Though the Guardians lost Sagira to Panoptes during their mission to locate the Infinite Mind's lair, they remained determined to stop Panoptes from bringing about the Vex's desired future. With the aid of Ikora and her abilities, the Guardian was able to enter the Infinite Forest once again and find Panopte's lair, Infinity's Crown.
The Guardians battle with the Infinite Mind but find themselves unable to harm the Axis Mind. Just before Panoptes deletes the Guardian, Osiris himself and many of his reflections arrive to aid the Guardian. Using his power, Osiris stuns Panoptes enough that Guardian was able to harm the Infinite Mind's core using Arc charges. In time, the Infinite Mind was destroyed for good, stopping the Vex from merging reality into their dark future. Leaving the Infinite Gate, Osiris is reunited and reconciles with Ikora Rey but returns to the Infinite Forest to prevent any more Vex plots.
Such plots involved the Vex attempting to salvage themselves from the loss of Panoptes. When Osiris foolishly created a simulation of Dendron, Root Mind, in an attempt to control it, the Cyclops Axis Mind went rogue and made efforts to fill in the void left after the Infinite Mind's demise. However, the exiled warlock managed to contact the Guardians in time to prevent Dendron from taking any action. Traveling to the Simulated Past in the Infinite Forest, the Guardians were successful in eliminating the Root Mind once again.
Further, the Guardians made constant travels into the Infinite Forest, preventing any Vex experiments from bearing anything significant that would work against the Last City. One experiment involved the simulated Cabal Valus Thuun. After the simulation failed to prevent the Guardians from finding the Infinite Mind's lair, Thuun was resurrected as part of a glitch and continuously attempts to destroy the map, only to fail. Osiris contacts the Guardians again and has them eliminate Valus Thuun for good.
At some point, the Leviathan consumed a chunk of Nessus that contained a powerful Vex Mind, Argos, Planetary Core, which caused the world-eater to clog up and malfunction. Emperor Calus immediately called upon the help of the Guardians to destroy the Vex intrusion, where they succeeded and repaired the Leviathan. Calus saved the Guardians from being sucked into the Leviathan afterward, where he rewarded them for their efforts.
One year after the conclusion of the Red War and Vex's crippling losses in the Infinite Forest, a mass breakout occurred within the Prison of Elders, releasing many imprisoned Vex to roam the facility. According to The Drifter, the Guardians and the Last City have done so much damage to the Vex in recent years that they had consolidated their subtypes, providing an explanation for the singular (so far unnamed) collective that roamed Sol post-Red War.
Return of The Undying
Following the discovery of a Pyramid on Luna, which is revealed to be a remnant of the Darkness that brought about the Collapse to the Solar System, the Guardian had retrieved an unknown artifact from within the structure for Eris Morn to study. Soon enough, the artifact emitted a signal that reached deep within the Black Garden. Following Eris' suggestion, the Guardians formed a Raid team to trace the end of the mysterious signal. Breaching into the Black Garden once more, the Guardians encountered a Vex Mind known as the Consecrated Mind, that they tailed through a winding labyrinth and destroyed it. Soon, they found remnants of the Darkness' presence left in the Garden that the Vex were attempting to harness with the Sanctified Mind. Despite its power and manipulating the timeways, the Guardians managed to destroy the Sanctified Mind, halting the Vex's attempts to harness the Pyramid's power.
Despite the victory in destroying the Axis Mind and bridging a new portal to the Black Garden, Sol Divisive Vex were pouring from the Black Garden and invading the lunar surface. As the Guardians dealt with the Nightmares and the Hidden Swarm, the Vex began to take measures to claim the Moon for themselves. Realizing that the Vanguard's foothold on the Moon is threatened, Eris Morn called upon the Young Wolf to investigate the Vex invasion and report to Ikora Rey. The Young Wolf reported that after they destroyed multiple Vex incursions on the moon and they managed to enter the Black Garden itself, allowing them to disrupt the flow of Vex platforms by assaulting the gate network to the moon. Between the Young Wolf's assault and other reports from the moon, Ikora had determined that The Undying Mind had once more been reactivated by the Vex and was continuing with its primary directive to retake control of the Black Garden and restore the Black Heart at its core. Furthermore, Ikora Rey noted that the Undying Mind itself learned from its previous mistakes, causing her to theorize that the Mind is hiding between timelines to avoid destruction. Resolving to defeat the Axis Mind, the Warlock Vanguard requested the Guardians to gather more data to develop a plan for when they will confront the Undying Mind again.
Some weeks later, after Zavala and Ikora managed to destroy dozens of Undying Mind copies, Ikora instructs the Guardian to do the same. Using a beacon Ikora created, the Guardian forms a team to combat the latest Vex Offensive and use that opportunity to breach into the Black Garden. After hacking into the Vex network, destroying scores of Vex forces and pushing forward, the Guardians set up Ikora's beacon to pull one of the Undying Mind's copies out of the timeways, then to destroy it. The beacon proved a success, forcing the Undying Mind to appear, and the Guardians face off with the Axis Mind once more. After an arduous struggle, the Guardians managed to breach through the Undying Mind's defenses and destroy the copy. However, as this was just one of a possible thousand copies, the Guardians understand that a lot more work is to be done in the mission to destroy all the Undying Mind's copies.
After an exhausting campaign, the Guardians were successful in destroying all the copies of the Undying Mind. However, upon finally destroying the true Undying Mind, the timeways over Mercury became disrupted. As a result, access to the Vex timeways became available to other factions. Taking advantage of this, a council of Cabal Psion Flayers seek to assume control of the timeways to undo their defeat during the Red War and create a better future for themselves. Seeking to prevent this, Osiris emerges once more to organize the Guardians to prevent the Cabal from perverting the timeways, preserve their reality and possibly save a legend, Saint-14.
During the past, after Saint-14’s last mission to find Osiris and prior to the Guardian's awakening, the Vex, in their desperate attempt to kill Saint-14, built Agioktis, Martyr Mind at Infinity's Siphon, specifically designed to kill the legendary Titan by draining him of his Light. However, the Martyr Mind would get into a skirmish with the Guardian who used The Sundial to travel through time to save Saint-14. As a result of this distraction, the Martyr Mind would manage to detain the Guardian instead, but releasing Saint-14 in the process, where it would be destroyed by the Titan it was designed to stop.
Due to the Guardian's actions, Agioktis, Martyr Mind failed in its specific purpose to kill Saint-14, thus changing the course of time where Saint-14 never died and bringing him to the present.
The Vex in their biological form are aquatic microorganisms known as radiolaria. Though Ikora Rey believes that this is not the true form of the Vex themselves, as she believes that if the Vex could manifest their consciousness in such a form, it would be able to take on other forms.  The "mind-fluid" inside each of their mind-cores is composed of a milky substance wherein radiolaria cells float; this centralized mind-core is also a localized receiver for each individual Vex "component" of the Nexus. Their aquatic origins are strongly implied through their architecture. Vex cells are noted entheogens and physical contact with Vex units can produce dangerous mind-altering effects. 
It is believed that Vex are not born or made, so much as converted. When Asher Mir was infected with Radiolarian fluid, his arm turned into a Vex construct. Kabr, the Legionless would have suffered a similar fate had he not used his Light to become The Aegis.
Emperor Calus describes the Vex as "cocoons" for "something greater". He also describes all the Vex previously encountered merely as gardeners, engineers and managers, and implies that Guardians have yet to encounter their true warriors.
The ultimate goal of the Vex is to remake all of reality in their image. Praedyth described the Vex as being motivated by a "Pattern," which drives the Vex to either reshape or destroy everything in their path. Osiris referred to the Vex's objective as "Convergence," an outcome where all life in the universe has been converted to a simplified, digital form. As part of this ideal future, the Vex seek to bring about a state where neither the Light nor the Darkness exist any longer. The Vault of Glass on Venus serves as a testing ground for the Vex to manipulate reality through ontological means.
The Vex have displayed an interest in studying the behavior and strategies of other species in order to further their own aims. At least one known programming is known to study its enemies, taking prisoners for observation and conducting a variety of experiments; examples include the Ishtar Collective scientists, Failsafe's crew, and later The Guardian.
As a result of having originated in the primordial reality preceding the arrival of the Light and Darkness, the Vex are unable to simulate paracausal forces or beings. However they have demonstrated the capability to either siphon or erase such forces through deduction  or by using ontological weapons, and consequently have a particular interest in understanding paracausality and co-opting paracausal forces for their own use where possible. When the Vex first encountered the Hive after Crota inadvertently released them into the Ascendant realm of Oryx, the Taken King, the Vex manifested an Axis Mind dedicated to understanding and utilizing the Sword-Logic. The Black Garden is another example of a Vex effort to harness paracausal forces for their own use, in this case by creating the Sol Divisive to worship what appeared to be a fragment of the Darkness and the Sol Progeny as its vessels for harnessing that power in conjuction with the ontological Vault of Glass. The pulse of Light emitted by the Traveler when it defeated Ghaul was apparently instrumental in allowing Panoptes, Infinite Mind to predict a future where Convergence was achieved, and to enact a plan to achieve that future.
Named individuals and mini-bosses
Vex Collective Leadership
Machine Worlds and Gate technology
It is thought that the Vex have embedded structures within every known celestial body, linked together in a massive trans-dimensional and trans-temporal gate network, which spans thousands of divergent realities all at once. Using this gate network in the present timeline, machinoforming engines are utilized by Vex Minds in the conversion of new worlds into massive Vex machines; Mercury was converted into a Machine World within days of the Collapse to house the reality-simulating Infinite Forest. Ostensibly, Vex strive to achieve Convergence by incorporating themselves into the fabric of the current universe itself, either through conventional or paracausal means. The Vault of Glass, a location on Venus where the Vex can ontologically manipulate reality at will, is potentially a testing ground for this power. This power is limited to the Vault, though Ikora hypothesizes that the Sol Progeny were meant to carry this ability into the rest of the universe. Both the Vault of Glass and the conversion of Venus are both currently undertaken by the Hezen Protective, though the process of the latter was drawn out for centuries for unknown reasons.
Overall, the Vex network is compartmentalized and operates in localized nodes called “subnets”, which can each work independently from one another. If one suffers, it will not affect the rest of the network as a whole. They all function differently, but work toward the same goal of Convergence. The Infinite Forest, and possibly the Vault of Glass, are their own subnets, where the former represents only a fraction of Vex’s overall power. 
The Vex display a mastery of teleportation, and use a variety of teleportation modes for transporting troops and resources. Entire squads of Vex can drop into combat zones anywhere in the system, their arrival preceded by shimmering angular patterns and clouds of mist. According to Ghost, the Vex are capable of teleporting between star systems in seconds. Minotaurs are infamous for using teleportation aggressively, warping in and out of existence as they close with enemies. Stationary warp gates are also used to transport Vex between distant locations. Weapons such as the Slap Rifle and Line Rifle utilize teleportation as part of their core mechanisms, drawing power from highly energetic and vastly distant sources.
According to simulations within the Infinite Forest, the first Vex structures on Mercury arrived via teleportation from some other location in space, and possibly time as well.
As machine intelligences with incredible amounts of processing power at their disposal, the Vex are capable of generating simulations of reality to a degree of accuracy and realism exceeding even the best efforts of Golden Age humanity. According to records from the Ishtar Collective, Vex are capable of generating simulations of real-world events with perfect fidelity and predictive ability — essentially running a parallel reality in their minds which is arguably indistinguishable from the "real" universe. Even lone Goblins have the processing power to nest such simulations up to 227 times through the simple expedient of simulating themselves along with their surroundings.  The predictive capacity of these simulations appears to be limited only to ordinary physics, as the Vex are apparently unable to simulate complex phenomena that are linked to a paracausal power. These include Guardians, and Oryx; in the latter case they were only able to bootstrap a simulation of his original incarnation as Aurash. Warminds are also complex enough to resist simulation, at least by a single Vex unit.
The Infinite Forest within Mercury is perhaps the most impressive example of Vex simulation technology, being a massive "reality engine" capable of simulating countless variants of past, present and future realities. These simulations can be entered by non-Vex through a gateway on the surface of Mercury, and are "real" enough such that intruders can be damaged by attacks from simulated Vex or other entities within the Forest. Simulations can somehow leave the confines of the Infinite Forest if left unchecked, and can achieve sentience to operate independently.
The Simulations appear to be fundamentally connected to their real world selves as being tortured in the simulation would inadvertently effect the real world counterparts, even the risk of erasure seems to cause some sort of mental hazard to the physical targets, they would even commit suicide or go insane.
As a collective intelligence spanning across alternate realities, the Vex are intrinsically tied to the Corridors of Time that they can traverse through it in a manner similar to time travel; the Precursors and Descendants subtypes having originated from the past and future respectively, and numerous Vex units have titles or functions that allude to an ability to manipulate time. Skolas, Kell of Kells attempted to leverage Vex time-travel technology to pull the entire House of Wolves through time from the past to the present. However, according to Sister Faora of the Cult of Osiris, the Vex may not be capable of "time travel" as is commonly understood; if they were, she claims, neither the Guardians or any other obstacles to the Vex would still exist.
While hacking into a major Vex terminal, the A.I. Failsafe was captured by the Vex in the network; by the time the Guardian retrieved her, she explained that a decade had passed inside the network despite only a few minutes passing outside as time works differently between the two.  On Nessus, the Vex have apparently also engaged in spacetime engineering and "folded" the dimensions of normal spacetime, adding 6 new dimensions to the 4 dimensions of the spacetime continuum and making past and future interchangeable from the present moment on the planetoid. Certain Vex Minotaurs on Nessus and in the Infinite Forest are equipped with "Temporal Shielding," which will retroactively eliminate projectiles as if they were never fired at all.
According to the Drifter, Vex weapons retrieved from destroyed Vex no longer function.
The Vex are all connected to one another in a massive hive mind, but individual Vex units called Axis Minds act as leaders by storing all information necessary to complete a particular goal, freeing up individual Vex to pursue local tasks while the Axis Mind can plan globally. This creates a centralized weakness for the Vex, but they seem to consider it worth the risk. The Vex are divided up into different programming collectives, each with a different set of directives intended to advance the Vex race as a whole. Whether the Vex in question are devoted to engineering projects, full-scale war, or religious devotion, all Vex are united by a single, unfathomable purpose.
List of appearances