Pariahs, also known as blacksouls, psychic nulls and the soulless, are entities that have no presence in the warp. The most commonly known instances of Pariahs are the Imperium's Culexus Temple assassins and the Sisters of Silence of the Adeptus Astra Telepathica. Pariahs are the antithesis of Chaos as their being does not have any presence in the warp and indeed radiates a sense of unnaturalness and unease that is uncomfortable to living creatures and can be painful or even lethal to psychically sensitive beings such as Eldar or Psykers.
Pariahs are believed to have been created and seeded into the human population by the Necrons as part of their plan to remove all taint of Chaos from the galaxy. Recently, the forces of the C'tan known as the Deceiver have created a new variety of Necron Warrior that is a terrible blend of machine and organic components, forged from Pariahs and named after them. These Necron Pariahs are undoubtedly the first glimpses of the C'tan's ultimate plan for the galaxy.
The Pariah gene is passed on as is any other gene, or occurs through random mutation, just as those genes that cause susceptibility to the Psyker mutation. Pariahs are infinitely rarer than Psykers and make up a negligible proportion of the population, with maybe one individual per planet arising every generation, and they generally die young as their aura of disgust and nausea turns other living beings against them. Still, a few Pariahs survive to become servants of the Imperium and are often used as shields against the warp by Inquisitors, particularly those of the Ordo Hereticus, whose task it is to deal with the Witch and the Psyker. As stated earlier, the entirety of the Culexus Temple of assassins are Pariahs and they use their curse to become some of the deadliest psyker hunters in the Galaxy.
There are no known instances of Pariahs among the nonhuman races of the Galaxy.
Similar to Pariahs are "Blanks", also known as "Untouchables", who are able to block out psychic effects within a certain area. This "field" also projects a sense of fear or revulsion towards the Blank on anyone close enough to be affected1. A Blank often may not be aware of their own powers and may not be able to control them1. If these effects are directly connected to the Pariah gene, or some mutation of its effects is left unknown. However, blanks have a notably lesser effect on psykers than do Pariahs.
The largest collection of untouchables outside the Officio Assassinorum or the Sisters of Silence was the group known as the Distaff. Created by Inquisitor Gregor Eisenhorn of the Ordo Xenos, it had about two dozen members. It was used as a resource pool available to Eisenhorn and his Inquisitorial associates, with its members typically being seconded to the staff of various Inquisitors for the length of particular investigations. The Distaff was destroyed circa 386.M41.
There is only one known Black Pariah to ever have existed; Spear, a Chaos-Assassin who lived during the Horus Heresy. His abilties and powers were so potent that it was reckoned he would have been able to kill the mightiest psyker to have ever lived, the Emperor. It is unknown if this Black Pariah was the product of a fluke birth, or the tamperings of Clade Culexus, but regardless he was able to turn a target's psionic force back upon itself, manifesting the target's own power to destroy the target, the ultimate counter-psyker.2
- Dorian Black - Veteran Sergeant of the Cadian Shock Troops, then recruited to Eisenhorn's warrior band
- Jeremiah - Follower of Daemonhuntress Ivixia Dannica of the Ordo Malleus
- Alizebeth Bequin - Leader of the Distaff, associate of Inquisitor Gregor Eisenhorn of the Ordo Xenos
- Wystan Frauka - Associate of Inquisitor Gideon Ravenor
- Ferik Jurgen - Aide of Ciaphas Cain, who served in the 597th Vahallan regiment along with several other Imperial Guard regiments.