"While vile mutants still draw breath, there can be no peace. While obscene heretics' hearts still beat, there can be no respite. While faithless traitors still live, there can be no forgiveness."
— Verse I of XXV of the Silver Skulls Space Marine Chapter's Catechism of Hate

A mutant Chaos Cultist of Nurgle

Mutants are the millions of people across the Imperium of Man who have been deformed from the baseline human phenotypic state by genetic mutation. This mutation can be caused by environmental factors or by exposure to the raw psychic power of Chaos. These people are destined to become the outcasts and lower classes of Imperial society. They are shunned and are often hunted down and killed as the Imperium has little tolerance for any who deviate from the perfection of the baseline human form in mind or body. Mutation is actually considered a heretical crime against the Emperor of Mankind by Imperial authorities because of its connection to sympathy or worship of Chaos.

Human mutants are often terribly misshapen creatures, abominably deviating from the normal human form. On the other hand, not all mutants are degenerate beasts; many only bear a few extraordinary traits setting them apart from the rest of Mankind. While many mutants are born mutated as a result of their ancestors' exposure to mutagens like radiation or extreme planetary environments over many generations, exposure to the psychic energies of Chaos can also lead to rampant mutation. Because those who secretly worship the Chaos Gods as Chaos Cultists are known to be granted mutational "gifts" by their dark masters, physical mutation can be an indicator of inner spiritual corruption by Chaos. This is another reason that all mutants are considered suspect by the Imperium's authorities and are greeted as general social pariahs by almost everyone else across the human-settled galaxy.

Navigators are also considered mutants, but were actually intentionally created through the use of genetic engineering in the distant past, during the Dark Age of Technology to make it possible for Mankind to use the Warp-Drive for interstellar travel. Because they are absolutely vital to the Imperium 's commerce and defence, they, alongside Imperial Sanctioned Psykers and certain species of Abhumans, are the only officially-tolerated form of mutants.

Life in the Imperium for Mutants

Various Mutants

Ordo Hereticus pict-file displaying the menagerie of mutants encountered by the forces of the Inquisition

On many Imperial planets, mutants are quickly abandoned by their parents and have to quickly learn how to take care of themselves. They are almost always the worst off people in imperial society. It is very rare to find a world that will tolerate them and not discriminate against them. These worlds are a paradise for mutants compared to most worlds of the Imperium. Desperately seeking some form of acceptance, many mutants join rebellious cults. Most of these cults simply condemn the faults of imperial society but others worship chaos and plan rebellion. These cults easily corrupt mutants due to the discrimination they have suffered. On most worlds mutants are not allowed to carry weapons for fear of rebellion. The weapons they do come to possess will often be primitive chains, knives, stubbers and slug-throwing revolvers.

Mutant Rebellions and Witch Cults in the Imperium

The existence of "accepted" mutant populations (where the direct touch of the Warp is not evident) has always been a two-edged sword for the Imperium's authorities. Such unfortunates are often vital to economic operations, but they represent both a problem for civil order and a ready source of rebellions, riots, and cult activity. The history of many worlds is rife with such uprisings, and such conflicts are always bitter and merciless affairs. While Imperial Law and the Ministorum Creed protects the Imperial citizen from the worst privations of oppression on most worlds, those not classed as fully human enjoy no such defence from brutality and exploitation by those in power. The situation is worsened because most "normal" Imperial citizens fear the mutant as an unclean, unnatural, and inherently tainted thing, and many mutants return this hatred with interest.

Mutants are often exiled to hellish conditions such as those found in the deep rad mines of Sepheris Secundus or the choking fumes of Solomon's chemworks. Vilified, exploited, and outcast from the comforts of society, Abhuman and mutant populations can prove a fertile breeding ground for all manner of heretical beliefs. Anything that offers some sliver of solace, acceptance, or the chance to strike back at their oppressors will find ready converts. The most dangerous of such outlawed and secretive sects have wyrdlings and witches at their head. Mutants, particularly on worlds where there is a lingering warp taint, can have a much higher inherent incidence of psyker potential than the general human population of their given world. This problem is further exacerbated because given the mass of physical and mental distortion among their fellows, and the general antipathy among the abhuman castes toward the authorities, it can be much easier to hide a psyker’s gifts. Also, most who do not willingly succumb to the harvest of the Black Ships are forced to flee into the industrial wastes or the shadows of the underhive. Given such a dangerous and fearful life, it is common for their powers to grow should they survive, hunted and harried, their hatred for the Imperium inflamed by their ordeals.

While some rogues and witches revert to a solitary, almost bestial state, many mutant witch-kin gather followers about them, founding cults in their own name. On isolated Feral or Feudal Worlds, such witch cults are a source of dread, shrouded by superstition and false belief. In the burgeoning clamour of the Imperium’s heartlands, these witch–kin commonly sink to the depths, cowing dregs, abominations, and outcasts into submission with the brutal display of their powers. In rarer cases (and if the psyker is subtle and powerful enough), the most dangerous will infiltrate the hive above. Although often small in number and limited in scope, witch cults can prove extraordinarily dangerous if left to fester unchecked, adding power to a mutant uprising or becoming doorways to horrors from beyond.

Imperial Hatred of Mutants

"Twisted in flesh is twisted in soul."
— Abbess Sevencia of Sisk

A pict-capture of a Mutant-scum

The deep Imperial hatred for mutants and deviation from the standard physical human form is rooted in the earliest days of the Horus Heresy. During the Emperor's Great Crusade in the 30th Millennium to reunite the scattered colony worlds of humanity under the aegis of the Imperium, mutants were accepted and used as part of the Imperial Army, formed into their own squads or mixed with the ranks of the regular troops. However, after the Horus Heresy, mutants were outlawed by the High Lords of Terra for the part they had played in that terrible rebellion as the favoured servants of the Dark Gods. The post-Heresy association of most mutants with heretical and Chaos Cults has only cemented this hatred of them by the majority of the human population of the Imperium.

Psychic Mutants

Mutant Mob

Horde of Chaos mutants

There are many types of mutations and some affect the mind rather than the physical body, producing individuals with the ability to access the psychic energy of the Immaterium and use it to reshape the physical world. These psychic individuals always run the risk of becoming a host for the malevolent entities dubbed daemons that inhabit the Warp. These mutants are generally referred to as psykers in Low Gothic and they are among the most feared of human mutants. Humanity is not a naturally psychic species like the Eldar or the Orks and the ratio of physical to mental mutation among humans is approximately 1000:1, or 1000 physically mutated individuals for every one born with psychic abilities. Psykers are not left to live out their existence like most mutants but are taken from their homeworlds by the Imperium in the Inquisition's Black Ships to be trained by the Adeptus Astra Telepathica since they are considered far too dangerous to be allowed to exercise their abilities without proper Imperial conditioning. The training of Sanctioned Psykers by the Imperium allows them to be used in battle, to fuel the power of the Astronomican by sacrificing their lives to help the Emperor maintain that great telepathic beacon of interstellar travel or to serve in the choirs of Astropaths who telepathically communicate between distant worlds.

They are tested for aptitude by the Adeptus Astra Telepathica and the dangerously unstable or those deemed too mentally weak to protect their minds from daemonic possession are executed immediately. The survivors are taken in the infamous Black Ships of the Adeptus Astra Telepathica to be transported to Terra for their training. Some will eventually serve in the roles mentioned above or are even assigned to the service of the Astra Militarum. The luckiest psykers may be discovered by and adopted into the Chapters of the Space Marines where they become Librarians. Some may even eventually be accepted into the retinue of an Inquisitor as an Acolyte and eventual Throne Agent.

Psykers wield many and various powers, including the ability to gaze into the future, to shoot lightning out of their hands, to control the actions and minds of others and, most dangerously, to open portals from realspace into the Warp. The Warp is inhabited by many horrible and powerful entities such as daemons and the Enslavers. Psykers are like lights in a dark cave to these entities who can see them when they use their power and who desire an entry into the physical universe where they can unleash great mayhem among mortals. Therefore, whenever psykers use their powers they are at risk of possession by these Warp entities. A possessed psyker acts as a portal for daemons into the material world and may become a horrific daemonhost himself, spreading the corruption of Chaos wherever he goes. As more daemons come through the portal, they tear open the gateway further, slowly pulling a portion of the physical world into the Immaterium until reality begins to warp and reform under the strain of Chaos. Untrained psykers have no hope of survival against such an attack, and it was the occurrence of such tragedies when uncontrolled human psykers first began to appear at the end of the Dark Age of Technology that helped bring on the terrible destruction that consumed human space during the Age of Strife.

Not all who are touched by Chaos sought the attention willingly. The raw stuff of Chaos permeates the fabric of reality, warping and twisting it on a whim. Inquisitors and others who deliver Imperial justice hunt down and kill mutants as part of their duty to keep the foul taint of Chaos from destroying all that their God-Emperor has built. Even being a loyal citizen does not spare these mutated people from the purging fires of judgment. This can easily be seen as a betrayal to the mutants. With nowhere else to turn, they will seek each other out and devote themselves to the Dark Gods.

Khorne's forces have perhaps more mutants than those of any of his brothers among the major Chaos Gods, for many find it an easy path to channel their hate into battlefeld fury. Many of their twisted mutations lend themselves to combat as well. Razor claws replace hands, muscles triple in mass, acid blood seeps from wounds, and more. All these blessed improvements find favour with the Lord of Skulls, as all are valuable traits for the battlefeld. A mutant with such blessings and a heart full of rage is a tool Khorne can use, but even one without such useful mutations is welcome as long as the fire within the altered form burns for blood and skulls. The Blood God offers mutants the power to exact vengeance on the minions of the Corpse God that turned their backs on them, and this power is often eagerly accepted.

Other Races and Mutation

The powers of Chaos also produce mutation among the members of other species that are capable of being corrupted by it, but Mankind, with all of its psychic flaws and weaknesses, has always been particularly vulnerable to the temptations of Chaos and the mutations it brings. Among the allies of the T'au, the species known as the Kroot possesses the in-born ability to alter their own genomes and transform their physiology following the consumption of their enemies' bodies, gaining phenotypic traits that may add to their fitness as individuals and as a species. Though whether this is true mutation simply an atypical feature of the Kroot's natural genome is unknown to the Genetors of the Adeptus Mechanicus.


  • Black Crusade: Core Rulebook (RPG), pp. 20, 25, 50, 360
  • Black Crusade: The Tome of Blood (RPG), pg. 17
  • Dark Heresy: The Disciples of the Dark Gods (RPG), pg. 57
  • Warhammer 40,000: Rogue Trader (1st Edition), pp. 52-57
  • Warhammer 40,000 Rulebook (6th Edition), pp. 148, 158, 172-173, 177, 180, 218-219, 232, 404-405