From Destinypedia, the Destiny wiki
The Vex are a cyber-organic species as ancient as the Universe itself. While individual Vex units are robotic in appearance, they are merely walking tools for radiolaria, microscopic organisms suspended in Vex milk that contains the species' collective intelligence. The Vex are capable of great feats of engineering such as reconstructing entire planets like Mercury and Nessus into their Machine Worlds, portal-based space travel, data processing and timeline manipulation on a scale impossible for humanity, but lack language, thought and sentience in the human sense of those words. They cannot be conciliated or reasoned with, and are hostile to every other lifeform but their own.
The Vex have been present in the Solar System for billions of years, predating humanity; their sophisticated and watchfully guarded structures can be found on multiple planets, including Venus, Mars and Io. Some Vex locations, such as the Black Garden or the Vault of Glass, are artificial realms existing outside of normal space and time.
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.
The Vex originated in the "flower game" conducted between the Light and Darkness in the primordial "garden" that existed prior to the creation of the universe. All of these games would end with a single, self-sustaining pattern emerging and dominating the entire simulation. This was pleasing to the Darkness, but was irritating to the Light, which desired that the game produce endless novel patterns instead.
When the Light and Darkness began to war with one another, initiating the beginning of the universe, the patterns from the flower game escaped into it. In the initial hot state of the universe the abstract patterns existed as quantum fluctuations, before eventually creating a more stable substrate for themselves in the briny seas of the first worlds to form in the universe, the radiolaria. This was the origin of the Vex as they would later come to be known, and from this point forward they were driven to once more totally dominate the reality they found themselves in, though operating on "outdated" rules that did not account for the paracausal powers of the Darkness or the Light.
The rest of the Vex's evolutionary history is a matter of speculation, but Clovis Bray I hypothesized some likely intermediate steps during his studies of the Vex structures around 2082 Volantis. The Vex developed in extremely high energy environments and competition and predation were not optimal strategies. Instead, the group signalling between the radiolaria formed the basis for the evolution of a swarm intelligence. The radiolaria developed crude armor, possibly hydrogel or silica plating to shield themselves from intense cosmic radiation, allowing them to remain close enough to the surface to directly feed off this plentiful energy source. From here, the Vex constructed and developed ever more complex structures, storing the information in the patterns of the radiolaria colonies themselves. Their microscopic nature allowed the Vex intelligence to deduce and experiment with quantum and high energy physics early, while the radiolaria themselves became, in essence, microscopic tool users.
The Vex developed rapidly, and at some point in their development in the early universe, developed mega-structures around the shortlived hypermassive stars their planets originated around. These structures artifically extended the lifespan of these stars, allowing their use to 'forge' heavier elements that would have been otherwise fantastically rare in the early, low metal universe. 
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.
At some point, Clovis Bray I, the patriarch of the Bray family and founder of the Clovis Bray corporation, arranged for a Vex to be stolen from the Ishtar Collective and transported to his research site on Europa. This Vex then built a gate leading from Europa to 2082 Volantis, a blue giant star system in which the star had been surrounded by Vex megastructures. Clovis I's ensuing research into Vex radiolarian fluid and the mysterious paracausal power he called "Clarity" resulted in a breakthrough in the development of exominds.
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
Sometime before the events of Destiny, the Guardians Kabr, the Legionless, Pahanin, and Praedyth ventured into the Vault of Glass on Venus, a major confluence of the Vex network. Inside, they were quickly thwarted by the Templar and its Gorgons. Pahanin managed to escape, but Kabr was assimilated after giving his Light to fashion the Aegis, while Praedyth was captured and trapped outside of time.
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. This massive, if ineffective, offensive against the Cabal was an effort by the Vex to bar entry to the Black Garden, which the Vex were being summoned to for a then-unknown purpose. Upon successfully infiltrating the Black Garden, the Guardian discovered a collective of Vex dedicated to worshipping an entity within the Garden known as the Black Heart, an aspect or construct of the Darkness. This seemingly-uncharacteristic behavior was later thought to have been as rational as everything the Vex do; they simply determined that worshiping the Heart would be the most advantageous course of action. This hypothesis was supported by the presence of the Sol Progeny, a trio of Vex frames meant to serve as vessels for the Heart—and to use its power to further the ends of the Vex network.
Subsequently, a second group of Guardians would enter the Vault of Glass, seeking to further break the Vex's power following the destruction of the Black Heart. The Aegis—having been designed specifically to counter the reality-bending capabilities of the Vault’s denizens—allowed these Guardians to escape the fates of their predecessors, fight their way to the core of the Vault, and engage and destroy Atheon, Time's Conflux, the Vault's overseer.
The destruction of the Heart had caused the Black Garden to become a part of normal spacetime, with several entryways on and beneath the surface of Mars. The Undying Mind, an ancient Vex Hydra, would later attempt to seal the Garden away from normal spacetime once more, to secure it against further intrusion. Following the destruction of Crota on the Moon, a strike team entered the Garden and destroyed the Mind, stopping its work—though, true to its name, it would eventually return.
The Taken War
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...".
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.
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 invited 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.
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 a Pyramid Scale left in the Garden that the Vex were attempting to harness its Darkness with the Sanctified Mind. Despite its newfound paracausal power, 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.
Having failed to take control of the Vex timeways with the Sundial, the Red Legion, under the leadership of the Psion Flayer Amtec, enacted a last resort plan to crash the warship known as the Almighty into the Last City. To stop the Almighty, Guardians began arming the Warmind Rasputin on Earth, the Moon, and Io. Operations on Io attracted the curiosity of Vex forces, much to the chagrin of Asher Mir, who would complain to Ana Bray about "stirring up" the Vex. In addition, Vex responsible for machine conversion managed to excavate their way into the Seraph Bunker outside the Pyramidion, requiring it to be cleared out frequently for it to maintain a connection to Rasputin's mainframe.
Following the arrival of the Pyramids and the deactivation of Rasputin, the Vex would begin to study the new arrivals first on Io. As Eris Morn and the Drifter attempted to contact the Pyramids, the Vex would take interest in these Darkness-harvesting operations and attempt to sabotage their efforts, often deploying Champions to steal any of the coalesced and bloomed darkness for further analysis. One of the Pyramids reciprocated this study, scanning the Pyramidion on Io in preparation for an incursion into the structure to learn the secrets of the Vex. When Asher Mir learned of this, he ventured into the Pyramidion to protect it from the Pyramid, initially encountering resistance from the Vex, who later seemed to welcome and simply observe him.
By the time of the Festival of the Lost, the Haunted Forest Iteration who come around in the Infinite Forest again, the Vex are aware of the several parties boarding the Dreadnaught and salvaging what they can from it. The Vex would then simulate these events in order to steal what the Fallen have found. 
During the conflict between the the Guardian and the House of Salvation on Europa, Eramis, Kell of Darkness sought to wipe out her enemies with an invasion of Vex unleashed from the ancient portal to 2082 Volantis constructed by Clovis Bray. She activated the portal, releasing Belmon, Transcendent Mind and waves of Transcendent Hydras. After a lengthy battle, The Guardian was successful in destroying Belmon and sealing the portal, however many Vex would escape and attack Riis-Reborn. In addition, The Guardian is unable to stop Eramis from draining the massive pool of Radiolaria at the portal and sending it to Atraks in the Deep Stone Crypt (raid) to forge her Exo bodies.
Following the Guardian's trials with the Cabal, the Vex somehow have plunged the Last City into an endless night, threatening the safety once found beneath the watchful presence of the Traveler. To combat the Vex's latest intrusion, Ikora and Osiris have the Guardians call upon an unlikely ally: Mithrax, Kell of the House of Light and one of the last of the Sacred Splicers. As a member of this order, he possesses the knowledge needed to combat the Vex technology that ensnares the Last City.
The Guardian managed to locate Mithrax on Europa after he was attempting to grant safe passage to Eliksni refugees fleeing from the House of Salvation but was ambushed by the Vex. After meeting with the Kell, Mithrax asks the Guardian to aid him in "blinding" the Vex so he can lead his people to safety. The Guardian agrees and, using a special device of Mithrax's, they enter into the Outer Nexus of the Vex Network. With Mithrax's guidance, they manage to slay the Curator in charge, bringing back a sample of its living code for study, and escape before the Vex could retaliate. Sharing a common enemy and understanding that Mithrax and his house are different than the other Fallen, Ikora offers Mithrax and the House of Light safe haven with the Last City, to which the Kell gratefully accepts.
With Mithrax's guidance in training them as Sacred Splicers, the Guardians make progress in continually breaching the Outer Nexus and slaying various amounts of Oppressive and Subjective Minds, bringing back their codes to study and hopefully find a solution in ending the Eternal Night the Vex have placed over the Last City.
For weeks to months, the Guardians constantly breach into the Vex Nexus domain and battle against a number of subjective minds, gathering data that could explain the nature of the Endless Night. From this data, both the Vanguard and Mithrax discover that the true architects of the Endless Night are the Taken Vex Mind, Quria, the Dreaming Mind and its master, Savathûn, the Witch Queen. With this knowledge in hand, Osiris delves into learning all they can about the Witch Queen while Mithrax continues to pinpoint Quira's position, allowing the Guardians to corner it. Eventually, Mithrax was able to gain Quria's position and trap it, giving the Guardians' the chance to destroy it. After a long battle to ensure the Last City sees a new dawn again, the Guardians succeed in destroying the Dreaming Mind despite its use of the Vex simulations and Taken powers, dealing a crippling blow to Savathûn. Despite the Dreaming Mind's destruction, the Endless Night hasn't dissipated yet but the Vanguard and Mithrax believe it will slowly fade away given time.
The Vex do not have a subjective consciousness as understood by humans. The Vex pattern of thought does not include semiosis, which is the use of symbols to represent ideas, concepts and meanings in human language and thought. The Vex instead simulate all phenomena within themselves to express and manipulate ideas. Whereas a human when touching fire will use symbols to represent this stimulus, process them and produce an output to extinguish the fire, the Vex pattern of thought is adapted so that, if it is burned, the destructive imput of the fire to the pattern inherently causes a repertory output to extinguish with no middle process. The Vex do not necessarily know why they do what they do, they simply do. As the Vex mode of thought is entirely based on the manipulation of internal simulations, the Vex swarm mind has very little or perhaps no ability to distinguish between simulation and reality; there is merely the internal model, and the external that must be changed to match it. There are no individual experiences in the Vex collective, and perhaps nothing analogous to sentience as well—each instantiation of the Vex is a fractal mirror of the master pattern that makes the Vex, leaving the whole able to occupy and utilize any substrate for their processing. The Vex are capable of manifesting consciousnesses as simulation, as part of their interrogation of reality, and even use these simulations to achieve their goals in certain situations.
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. 
According to notes taken by Clovis Bray I, the dynamic mobility of radiolaria within their fluid environment renders them exceptionally well-suited for performing certain difficult calculations. He also noted that the Vex language as embodied within radiolarian fluid does not involve semiosis, or the use of symbols; instead of utilizing "placeholders" for concepts, the Vex directly mimic or simulate concepts or phenomena as they communicate about them to one another. The asymbolic nature of Vex language is the fundamental difference between Vex cognition and human cognition.
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. This also explains why Radiolarian fluid deals damage when stepped in. In the opening cinematic for Season of the Undying however, Vex constructs are seen inactive in what is described as a "gestation lake", where Radiolarian fluid finds its way into constructs to bring them to life. It is possible that manufacture supplements conversion, or that newly-converted constructs may need to undergo additional processing before they can be activated.
It is stated that when Vex become Taken, that they can definitely feel it, including Vex constructs such as Asher's converted arm, that is is equivalent to ripping the essence from them. Asher even stated that Taking Vex would be suicidal and risky as the Vex infect everything they touch, their self-replicating subroutines would consume them from the inside out, whether they are ignore or it is part of a calculated risk is still unclear at the time.
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, but the exact details of that goal are ambiguous. 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. Savathûn believed that the Vex sought to dominate "every possible end state of the universe." According to Maya Sundaresh, a universe ruled by the Vex would be one in which every star is collapsed into a black hole and every new universe created as a result similarly conquered, and their combined processing power used to simulate and conquer every possible past, and these simulated pasts used to host and invade additional simulations in infinite recursion. As seen in the Infinite Forest, to ensure their 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.
In his studies of the Vex, Clovis Bray I noted that the Vex were so utterly adapted to survival and adaptation that any destructive input would automatically be used as a means to enable a self-correcting or reparatory response; an analogy he used was that, if a Vex unit were exposed to a fire, then the energy of that fire would be utilized in putting it out. This approach to existence permeates every aspect of the Vex, so much so that even their thoughts and language are intrinsically virulent when other minds and software are exposed to them.
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 predating the arrival of 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.
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.
Named individuals and mini-bosses
Vex Axis Minds
Vex Gate Lords
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.
According to notes taken by Clovis Bray I, Vex gates appear to lack meaningful structure or instrumentality, instead being a seemingly arbitrary arrangement of elemental metallic components. He speculated that a gate's structure instead serves as a kind of "password" that is recognized by some technology far away in time and/or space, which will manifest a gate only when the component pieces of the gate have been assembled in the correct shape. An AI analysis included in his notes shows that transport through a gate appears to be facilitated by a non-gravitating, geometric Ellis wormhole that can be traversed into another point in local spacetime, or a nearby parallel universe.
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 in the pockets of the universes that are being simulated.  Due to the nature of Vex cognition, they cannot actually distinguish between their simulations and reality, and only recognize that the two must match. 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.
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.
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