Unfortunately much of the game’s lore is hidden within the Grimoire cards.
Thanks to Reddit user KentsFood, he’s compiled information & lore about the Vex (mostly from the Grimoire), which you can read below.
The Vex are architects of ancient and complex structures on Venus and Mercury. Linked by a data network unlike any on Earth, they operate in unison, directed by a single unfathomable purpose.
Vex Programming: Hezen Corrective, Hezen Prime, Vega Prohibition, Aphix Invasive, Sol Divisive.
Bodies of animate metal with traces of living matter within, the Vex are an enigma, traveling through time and space with their gateways.
It is not clear if they have arrived here from the future, the past, or from another past or future. What is clear is that they represent a dire threat to humanity. They march with a singular purpose on the battlefield, driven by some unknown and unknowable intelligence, passionless and focused on completing their mysterious objectives.
The Vex transform the planets they occupy, terraforming inorganic landscape into massive computational structures.
To say we understand nothing about the Vex is a lie. We understand that they share a single mind, for lack of a better term, over million of units. For all we know, there could be hundreds of different minds. The Vex employ a number of different chassises, each having a number of different functions and, from what we understand, computational abilities. Many of the Vex Axis Minds: elite super Vex that contain instructions for a particular objective – leaving other Vex to focus on their tasks and leaving global planning for the Axis Mind – share similar structures with these units, and will be noted alongside that Chassis.
Goblins are the basic units. They do not take retreat, take cover, or falter. Unwavering, they will continues towards their objective until otherwise impeded. Headshots do nothing but enrage them, yet shooting the milky, protozoic substance at their core will dispatch them with ease.
Hobgoblins are specialised for sniping. Their eyes contain advanced optic sensors, their horns contain acute sensory modules that they use to fully grasp their surrounding enemies. Even stranger, Hobgoblins, when attacked, have a defence reflex that seals them in unbreakable stasis for a short amount of time.
Hobgoblins and Goblins have a milky substance at their core, which a record says is “Radiolarian.” Radiolaria are protozoa found in the ocean on Earth (for example, after the Traveler came they could be found on every other planet and moon, this cryptarch does not know), known for creating intricate mineral skeletons for themselves. Perhaps this means that the Vex use this substance for growth and repair.
Harpies (singular Harpy) are the fastest of the Vex, and capable of flight. They are often spotted in “flocks” on Vex scouting missions or on patrol. Harpies cannot move and fire at the same time, they must first stop and stabilise themselves before shooting.
Gorgons are found within the Vault of Glass, and have the shape of Harpies, though they appear to be members of the Sol Imminent (Descendants). The Gorgons possess ontological power; the ability to decide what is real and what is not. There is no countermeasure to this threat. If a Gorgon gazes upon a Guardian and determines him to have never existed, it will be so. Countless guardians have been lost to this unbeatable weapon.
Minotaurs are strong, but interestingly, they’re the builders of the Vex. Most of their computational power is devoted to constructing the various structures on Mars, Venus and Mercury suspected to extend through dimensions. Minotaurs are the toughest shells of the Vex, and will use their ability to teleport with aggression.
Most of the Vex Axis Minds are Minotaurs in structure. Gate Lords only appear in their physical form when summoned, otherwise they exist in a digital state. It is believed that the Gate Lords oversee travel between Vex Gates and their minds contain codes to other dimensions, times and places. A Guardian defeated Zydron, A Gate-Lord summoned on Venus, to retrieve it’s head for the Queen of the reef. The Prohibitive Mind was in charge of the Vex assault on the Cabal on Mars. It coordinated Gate entrances and Vex attacks against key Cabal positions, until it was destroyed by a Guardian.
A Guardian was able to enter the Black Garden, and there they found the Sol Progeny. “Progeny” means children or descendants, and the models of these three Minotaurs coincided with past, present and future models of Vex units: Sol Primeval, Sol Divisive and Sol Imminent respectively. These Axis Minds were believed to serve as relays to whatever it was the Guardians destroyed in the Garden. The most interesting, and most lethal, of all the Minotaur model vex Axis Minds was Atheon. Found in the Vault of Glass. Atheon’s functions are hard to describe, but it’s (believed to be) intended goal is not.
The Vex are suspected to be attempting to rewrite the Universe. To implant themselves so far forwards and backwards in time that they existed before all else and will exist until all else dies. Atheon controlled Vex Confluxes, believed to be extensions of the Vex Network. Atheon is basically the centre of time, dimension and space travel for the Vex, and his destruction could prove essential in dampening the Vex’s plans.
The largest mobile frame is the Hydra. Supercomputers, they can chew through data sent to it by all other Vex nearby in a matter of seconds. Not only this, but it boasts incredible fire power and a shield that absorbs all damage against it. When a Hydra is destroyed, the explosion it creates is powerful and deadly, but could be used to a Guardians advantage.
Only two known Axis Mind Hydra exist: The first being Sekrion. Sekrion was a Nexus Mind, in charge of overseeing the Vex Network’s implantation in the surface of Venus. Sekrion was likely in charge of relaying plans to Minotaurs around the planet on where to construct Confluxes and Nexuses. It’s destruction could halt the the Vex’s plans with Venus.
The other is the fabled Templar. Guarding the way to Atheon, the Templar and it’s Oracles had the ability to perceive any point in time and decide what should happen in something called The Ritual of Negation. During the ritual, the Oracles told the Templar what they believe the future should be in favour of the Vex, and the Templar made it so. Not only this, but it was fully surrounded (unlike most Hydras) by a impregnable shield, meaning it was impossible to damage. Guardians found a way to destroy it however, and it’s terrible reign over the Vault was ended.
Finally, the Vex have massive, immobile sentries called Cyclopses. Huge turrets to the Guardians with devastating void fire, they are believed to actually be sensors or beacons and that their weapon systems are secondary to their actual function: Either relaying instructions or involving Vex Travel.
Mentioned a few times above, different groups of Vex have different objectives, all eventually leading to whatever grand plan the Vex are working towards. The Hezen Corrective for example, seek out the Fallen House of Winter and aggressively campaign against it, build Confluxes and apparently show interest in Golden Age Ruins, all around the Ishtar region. Most of the Vanguards contact with the Vex has been with the Corrective.
The Hezen Protective is the next major subtype on Venus. They are a defensive unit, focused around the Citadel, A massive Vex Gate and the Vault of Glass. The Protective, as all Vex, are working towards a goal which is unclear to us at this moment. They could be reacting to something that has not happened yet, or to something that happened centuries ago. It is never clear with the Vex.
On Mars, The Virgo Prohibition are relentless agressive Vex in constant conflict with the Cabal. However, despite the Vex’s efforts, the Cabal have taken several key Vex gates and confluxes on Mars, and the Prohibition appear to be failing. Is it possible that the Vex made a mistake and misjudged an enemy? Or are they simply working towards something larger, more grand? As appears to be normal in this compilation of data, the Vex only create more questions instead of answers.
In the Black Garden, a subtype of Vex called the Sol Divisive protect and worship the Black Garden. Their function is unknown, but they must be important as the Garden clearly was instrumental to the Vex.
In the Vault of Glass, two additional Vex Subtypes were uncovered. The Sol Primeval and the Sol Imminent, Precursors andDescendants respectively. The Primeval appear to be from the past, built long before the Vex we know today, while the Descendants are the opposite. Advanced, future Vex. Does this mean that the Vex are unbeatable? That our future is extinction?
During a mission into the Archive, an old research bank in the Ishtar Academy, Guardians uncovered several research logs of a team of scientists studying the Vex. Their names: Esi, Sundaresh, Shim and Duane-McNiadh. They uncovered a Vex specimen running an extremely accurate simulation of the team itself, the sim mimicking the teams actions. They began to believe that they themselves were simulations and that the Vex were in control. The original idea to create the Warminds may have been born in that research facility as a way to “call for help”. It was believed the Vex would not be able to simulate the Warmind perfectly.
The researchers bodies were found at the entrance to the Archive, indicating they sealed it to stop something getting in, or out.
The Vault of Glass was discovered by a Titan named Kabr. He descended into the Vault, and fashioned armour out of the Vex he destroyed. Kabr is believed to have been responsible for the construction of the Relic, also rumoured to be hammered out of the shell of a Gorgon. The Relic has the same capabilities as a Gorgon (To decide what is real and what is not), so this rumour has merit. Since he was apparently unable to erase the Templar, Gorgons or Atheon, it is assumed he perished in the Vault, after relieving information of its whereabouts and danger to the Vanguard. Six Guardians ventured into the Vault and successfully halted Vex plans there, destroying the Templar and Atheon.
During the collapse, the planet Mercury was completely overrun by Vex. Once a beautiful, eden world Mercury sits covered in forgotten Vex structures. There is no life there anymore, so Lord Shaxx has been training Guardians there in the Crucible, for fighting in Vex structures.
The Black Garden is perhaps one of the more confusing Vex mysteries, and for the Vex that’s saying a lot. The Garden does not appear to be on Mars, yet Mars is where it is located. The Vex worship the Garden, but it is unknown whether they were the creators or the created of the Garden. Legends have existed of the Garden since the golden age, too complex for me to repeat here. The Progeny defended it, activating one unit at a time, indicating it’s power was not full.
The Garden could be a source of Vex Power, it could be a manifestation of the Darkness itself, it could simply be a form of Vex we had never encountered before. What is for sure, is that is destruction returned Light to the Traveler, and hinderance to the Vex’s infinite plans.