Psions are a race of psychically-powerful beings who were conquered and enslaved by the Cabal in the hopes of weaponizing their abilities. They now primarily serve as engineers, pilots and fire support within the Cabal military.
Ancient Psions practiced a form of ancestor worship, communing with the divine spirits of the dead through a Y-goblet that "cupped their spirits" and poured out their souls into new Psions. Worship involved daily rituals in which the Y-goblet was filled with offerings for ancestors, such as water to wash out their eyes, salt to roughen their skin,  or linen to bind their wounds. Other practices included physically drawing the Y-goblet on a nearby surface. Adherents believed that every other person, or at least Psions, had a spark of the divine within them, physically evident in their Y-shaped pupils. 
In prehistory, long before the Psion species joined the Cabal, a group of exceptionally powerful Psions known as the God-Thoughts dominated the species with their psychic abilities. They destroyed the Y-goblet faith for seeing divinity in every common person. Its suppression was so brutal that while the faith survived to the present, its practitioners still feared discovery and worshiped only in secret.
The Psions were assimilated into the Cabal empire either before or during Emperor Calus's reign. They were largely enslaved under indenture, but some were allowed to remain free.
The legendary, clairvoyant OXA Machine has been built, lost, and rebuilt many times in Psion history, passing down from civilization to civilization over the ages.  Its most recent iteration was destroyed by the Cabal, but rebuilt centuries later on Brand by Freeborn Otzot, a particularly brilliant Psion. When Umun'arath moved to destroy this newest version of the machine, Emperor Calus stopped her in recognition of Otzot's genius, and welcomed the freeborn Psion into his court as his Imperial Dreamer.
Late into Calus's reign, he attempted to grant freedom to all indentured Psions, but was overthrown before this could happen. Ironically, Otzot was one of the conspirators against him.
Psions have bald, veined heads, with a single eye surrounded by black trident-shaped creases. These eyes can be either blue or orange, and have distinctive Y-shaped pupils. Their eyes turn opaque grey once they die, and the Y disappears. Their faces have a series of holes above their mouths, possibly functioning similar to spiracles for breathing. Psions serving in the Red Legion have the tops of their heads exposed, even in harsh environments such as Mars, Io, and Nessus without any visible damage. This is likely done to enable them to utilise their psionic abilities more freely, though also implies that their skin is incredibly tough despite its fragile appearance. Psions have five fingers on each hand, though often their armor groups their middle and ring fingers into one. They are significantly smaller than their Cabal superiors on average. However, Kargen, the Technocrat, the Flayer Sisters, and Inotam, Oblivion's Triune are notable for towering over the Cabal under their command..
Psions seem to have a deep reverence for the lives of those around them, as their clairvoyance allows them to sense them in intense and mysterious ways. They feel the imprints of those around them, noting the powerful gleaming aura of Calus to be so blinding that they cannot see past it. They are unnerved by the Hive, because they appear to have empty minds besides their hate and need to survive. It is likely that Psions are naturally very social, as they have some ability to communicate with each other telepathically and will even combine their thoughts together in concerts in times of stress or necessity. This telepathy may not be wholly consensual or their higher level thoughts are broadcast to some degree, as some Psions will think in metaconcert if they want to keep a secret from their peers.
Within the Cabal Empire, Psions are second-class citizens at best and slaves at worst. They serve the Cabal as laborers, engineers, and mechanics. Psions have worked as pilots as well in their time of service. Their integral part in the Cabal military is seen through the extent at which they rely on the Psions. Maintenance passages in most of their ships and structures are often too small for Cabal to move through comfortably, and Interceptors are designed for use by Psions exclusively. Particularly talented Psions are trained to become Psion Flayers, masters of their incredible power and intellect. The full extent of their abilities is unknown, but they are thought to have been able to alter the orbit of Phobos.
Certain Psions are not born into slavery and are regarded with the title of 'Freeborn'. They are exceptionally rare in Cabal society and are of vastly superior social standing to others of their race, potentially being considered equal to other Cabal.
The strength of a Psion's attack depends on the type of Psion. An ordinary Psion will only be able to attack at point blank range, a Psion Operant will be able to launch a short-range attack, and a Psion Flayer will be able to send a psychic attack from quite a long distance. These attacks deal Arc (or electrical) damage, signifying their power over mind and (potentially) machine. Certain Psions are known to channel Void and Solar power, though this is restricted to Flayers observed in the Prison of Elders. Psions become much more dangerous during Nightfall Strikes, as they acquire a Void shield.
A sect of Psions belonging to the Red Legion utilize new Void-based abilities as well as Cabal Headhunters. A minority continue to use Slug Rifles, and a few elites use Cabal Slug Shotguns. These Psions have an upgraded version of their old wave attack, now referred to as a "rupture ability," which explodes and launches enemies into the air. They also have jetpacks, which they can use to maneuver and travel at high speeds. Red Legion Psions have the upper parts of their heads exposed.
The Loyalists have a special version of Psions called Councilors, which have special abilities used throughout the Leviathan raid. They float in mid-air and are surrounded by a shield that blocks all projectiles, but are still vulnerable to melee attacks.
List of appearances