"I can think of few greater xenos threats to the Imperium than that of the Genestealer. An apex predator possessed of intelligence and cunning that rival our own, they exist for the sole purpose of reproducing in vast numbers and sowing utter chaos in their wake."
— Inquisitor Kalistradi from The Nature of the Beast
Purestrain Genestealer

A Genestealer prepares to pounce on its unsuspecting prey

A Genestealer (Corporaptor hominis) is a bioform of the multispecies Tyranid race that was genetically designed by the Hive Mind for the infiltration of other intelligent species' settled worlds. The Tyranids are an intelligent, nomadic alien race governed by a collective consciousness known as the Hive Mind and comprising many different genetically-engineered forms.


Genestealer attack

A Tyranid Genestealer on the hunt

Few Tyranid creatures have earned such a terrible reputation or caused as much damage to the Imperium of Man as the Genestealer. Encountered long before the first tendrils of the Hive Fleets reached the galaxy, they were thought to be little more than another unusual and deadly xeno-form. It was only after the horrors of Hive Fleet Behemoth and Hive Fleet Leviathan that the Imperium came to realise their true purpose as highly advanced infiltrators for the Hive Mind of the most insidious kind. Hiding away on void ships and in the depths of Space Hulks, the Genestealer menace has travelled across the length and breadth of the Imperium, seeding themselves onto human worlds and subverting their populations. This perhaps is the greatest horror the Genestealers bring, as they can infect almost any lifeform with a "kiss," implanting some of their own genetic material into the host and taking complete control of its reproductive system. When the host gives birth to offspring, these carry with them the Genestealer's genes and over the course of several generations a new Genestealer is born, albeit with some genetic traits taken from its host: such as the human-like hands many Genestealer Hybrids encountered in the Imperium possess.

Cunning and independent, Genestealers are also one of the few Tyranid bioforms that can exist away from the nurturing and controlling influence of the Hive Mind, using their own innate intelligence and brood telepathy to form tight-knit groups. These groups can survive for decades or even centuries on worlds, hiding their presence and infecting more and more of the population until the time to strike arrives, usually coinciding with the arrival of a Hive Fleet and the wholesale invasion and consumption of the world by the Great Devourer.

Genestealer Physiology

Stealer Helmet

A typical Purestrain Genestealer specimen

Genestealers, like virtually all Tyranid organisms, are characterised by their six limbs and resilient carapace. They are bipedal and able to move with lightning speed on their reverse-jointed, clawed lower limbs. The upper sets of limbs are distinctly different, the foremost pair ending in razor-sharp claws capable of slicing through Tactical Dreadnought Armour (ref. MGP.Macragge. 1st Company.qv). Their secondary limbs are typically shaped like gnarled hands, allowing them to manipulate objects, climb and even operate simple devices such as touch-panels. The number of digits differs depending on the parent organism. Despite their dexterity, these secondary limbs are still more than capable of ripping a limb from its socket. The thickly-muscled tail appears to be vestigial, although could aid the balance and agility shown by all variations of the species.

The colour of the Genestealer varies depending on its parent Hive Fleet. Specimens have been reported ranging from bone-white to jet black. Perhaps the most successful strain of Genestealer is typified by a blue-indigo coloration. This strain has been encountered on numerous Space Hulks and is possibly specifically nomadic; bio-engineered purely to infect new hosts.

4497 genestealer.tyranids

A Genestealer's characteristically bulbous head

A Genestealer's head is characteristically bulbous and houses a disproportionately large brain for such a single-minded creature. Its jaws are lined with viciously sharp teeth, all designed for ripping and tearing; like other Tyranids they possess only incisors and no molars.

Their carapace, along with the density of their internal skeleton, typically thickens with body mass; a Genestealer whose host was Orkoid will typically be tougher than one born of Eldar gene-stock. Underneath this is the fibrous muscular sheath that can be compared to standard Imperial Flak Armour in terms of durability. These layers provide a considerable degree of protection; combined with their naturally tough physique it is possible for a Genestealer to charge headlong through a volley of Lasgun fire and survive. As with other Tyranid organisms, they typically have an open circulatory system with haemolymph flooding the intercellular spaces. This system is host to unnumbered phage cells, believed by the Magos Biologis of New Hallefuss research facility to be digestive systems. These allow them to feed on the nutrient-rich end product of a Tyranid invasion. Closer investigation shows the phage cells to have a dual purpose, acting in a manner similar to fibrinogens in the human bloodstream and clotting the liquids that seep from any wounds that the Genestealer has suffered (ref.MBfl277.anticoagulant.hellfire.qv).

Another physiological anomaly that Genestealers display is the redundant respiratory and circulatory systems inherited from their host species. Furthermore, they exhibit vestigial digestive systems. Some specimens even have complete stomachs, although these are superfluous given the efficiency of the phage cell. These expendable systems allow the Genestealer to sustain considerable non-lethal damage and still function. It is widely known by Imperial forces that those coming into conflict with Genestealers should direct their fire towards the thorax and abdomen of the beasts, as even with several extremities missing they are still highly dangerous opponents.

Thanks to the capture of live Tyranid specimens by the Draco Legion Chapter of the Adeptus Astartes, it is known that Genestealers are able to feel pain and react adversely to its application, either becoming incredibly aggressive or cowed into temporary submission. Genestealers have a tremendous tolerance for cold, allowing them to survive in the void of deep space, hidden within the bowels of the Space Hulks they typically infest. They are even able to survive in a vacuum for a short space of time. To truly exploit the space detritus it inhabits, a Genestealer has great longevity and also the ability to endure long periods without nourishment. A Genestealer may also enter a torpid state at will, lowering its metabolic rate dramatically, therefore allowing them to survive long periods of inactivity and hardship until new prey enters their lair.

Reproduction Cycle


A Genestealer Ovipositor as dissected by an Adeptus Mechanicus Magos Biologis

Genestealers reproduce by introducing their genetic material into a host from another intelligent species; this is normally a human, but can theoretically be any sentient humanoid race, including the Eldar or the Orks. The Genestealers have no true genders, and require a creature of any species, any gender to reproduce. The Genestealer will find a suitable host and hypnotise them into passivity using an effect induced with its eyes. The Genestealer then thrusts its long, whip-like tongue (which also serves as an ovipositor) into the body of the host, where it deposits its DNA in the form of a type of virus that infects the somatic and germ line cells of the host. Several hours later, the infected victim wakes up from the incident, with no wounds or any recollection of what happened. The new host of the Genestealer DNA will go on about its normal life, and eventually reproduce with another member of its species, thus siring or giving birth to a Genestealer Hybrid. The Genestealer reproductive cycle is truly cyclical, as an F4 hybrid will always spawn a purestrain Genestealer with a genome identical to that of the original Genestealer that infected the first host.

Newly born Genestealer Hybrids, although fundamentally Genestealers, will have characteristics inherited from the host parent. Thus a Genestealer Hybrid of human stock may have a vaguely humanoid head, or only two arms instead of the usual four, and its tail will be shortened or missing. A Genestealer of four or more generations of consistent human parentage would pass for a baseline human on cursory inspection, although a closer look would reveal bluish skin, sharp, pointed teeth and unsettling behaviors. The Ymgarl Genestealers on their homeworld exploited a large, semisentient leech-like creature called a Csith as their usual host. As a known exception, Csith always produce natural Ymgarl Genestealers rather than Hybrids, no matter what the parentage of previous generations.

Combat Capabilities


A Genestealer fighting a Space Marine Terminator

Genestealers do not rely purely on their deadly speed and razor-fine claws to defeat their enemies. They are possessed of considerable intelligence, comparable to that of Lupus fenrisii (Fenrisian Wolves), and are able to coordinate stealth tactics such as setting functional traps when hunting prey. It is postulated that they convey information telepathically since no other form of communication has been observed from them thus far. This "brood intelligence" is thought to be akin to the gestalt consciousness of the Hive Mind, only on a smaller scale. This enables the Genestealer brood to act as an autonomous unit, able to function light years away from the synapse control of the larger Tyranid creatures.

Much of the Imperium's information on the combat abilities of the Genestealer has been supplied by the 1st Company of the Blood Angels Space Marine Chapter. They have performed numerous expeditions into the depths of Space Hulks such as Spawn of Execration, Charybdis, Immeasurable Hatred, Sin of Damnation and Harbinger of Despair. Decorated with the Blood Star after his success in leading missions into the heart of two of the aforementioned Hulks, Sergeant Lorenzo of the Blood Angels has filed comprehensive reports on the tactics used by these aliens and the lethal threat they pose.

The Genestealer will not hibernate without in-depth familiarity of its surroundings, including the ventilation systems, sewers and other crawl-ways that permeate the Space Hulk's corridors. In this way they can use such knowledge to take advantage of unsuspecting victims, whose knowledge of the voidship's labyrinthine passageways are often woefully inadequate. This allows them to close incredibly rapidly, denying any opportunity to cut them down with ranged weaponry. Once the Genestealer is in close quarters, it utilises its incredibly durable claws on each forelimb, able to slice through bulkheads and cut through the chunkiest armour. Combined with the awesome strength afforded by the efficiency of the Genestealer's musculature, it is quite feasible for a Genestealer to rip its way through the side of a Chimera and get to the troops inside. Any returning survivors of a Genestealer attack are inevitably heavily armed, forewarned and well-trained, or have become a host carrying purestrain seed.

Although the characteristic claws of the Genestealer are its primary weapons, certain variations in the xenomorph's form have been reported across the galaxy. Long, stabbing talons occasionally replace the Genestealer's secondary limbs, and several specimens have been found on Ork-infested Space Hulks with thicker carapaces. In 234.921.M41, a captured Genestealer carried virulent, inorganic poisons and haemotoxins in sac-like pouches on its arms. Another known genus can shoot thick, barbed strands of sinew into their victims to keep them from moving freely as the Genestealer closes in for the kill. These "flesh hooks" are dispatched from the ribcage by a sharp intercostal muscle spasm, and can also aid the xenomorph in climbing walls and other vertical surfaces. Presumably these traits are either inherited in part from the host species, or bioengineered by the Hive Mind in its eternal quest for ever more deadly soldier-organisms.

Genestealer Sub-Species

Purestrain Genestealer

Purestrain Genestealers have the same basic arthopodal body structure as all other Tyranid species. They appear as roughly man-sized, six-limbed creatures with both the chitinous exoskeleton and endoskeleton common to Tyranids. Their can function as a bipedal using their lower appendages; a second pair have extremely sharp claws used for evisceration in close combat - these claws are sharp enough to hack through extremely well-armored enemies, such as Space Marine Terminators, with ease. The third set of limbs may also act as arms, though their nature can vary depending on the type of host species used to create the Genestealers or the needs of the Hive Mind. In addition, Genestealers are known for their agility and adept fighting skill. Genestealers were first encountered by the Imperium of Man on the moons of Ymgarl. After this encounter, more and more were spotted on large derelict starships known as "space hulks"- these ship-borne encounters being the subject of the aforementioned Space Hulk game. With the invasion of the Imperium of Hive Fleet Behemoth in the late 41st Millennium, it was discovered that the Genestealers were in fact a part of the Tyranid race. Genestealers perform two roles for the Tyranid armies: First, in the main Tyranid hive armies acting as assault troops; second, they can be found as an advanced force of a Tyranid Hive Fleet, preparing future planetary invasions and aiding biomass absorption through the use of their unusual reproduction method.

Ymgarl Genestealer


An Ymgarl Genestealer hybrid

Imperial researchers of the Adeptus Mechanicus have concluded that the Ymgarl Genestealer was a form of the species that separated from the main conglomerate of the Tyranids' Hive Fleet Behemoth several hundred Terran years ago and, having completely lost its psychic link to the Tyranid Hive Mind, had thus reverted to a feral state. Ymgarl Genestealers appear apparently different from normal Genestealers, which is also believed by the Imperials to be due to the complete separation from the Hive Mind, and generations of feeding almost exclusively on a native lifeform of the Ymgarl moons.

Genestealers are known to change over the generations. The different variations between broods can be quite marked, but Ymgarl Genestealers are truly unique because they possess the ability to alter their own flesh to react to incoming attacks or to change its colour like a chameleon, so as to blend into its surroundings and remain unseen until it strikes or flees. Their claw-tipped fingers can suddenly elongate and fuse together to form curved blades and barbed hooks or split apart into tentacles of sinewy alien flesh to slash or entangle victims who attempt escape. Under assault, their chitinous carapaces thicken and help absorb the energy of incoming attacks.

Some Imperial observers that have made contact with these creatures reported this strain's ability to change the colour of their skins, utilizing extreme light conditions to better go undetected. Such an extreme adaptation comes at a high price for this bio-form, as Ymgarl Genestealers must feed on large amounts of biomatter often. Moreover, a Ymgarl Genestealer's most distinctive feature is the mass of writhing tentacles in place of a fanged mouth, which they use to pierce their victim's flesh and better feed upon the blood within -- this strain's only source of real nutrients. When they cannot obtain adequate nourishment to feed their raging metabolisms, they will be forced to enter a state of dormancy or otherwise starve to death. Once in this state they must wait until something living and of fresh blood passes near enough to disturb their dreamless sleep.

The origins of the Ymgarl Genestealers remain a mystery to Imperial savants, for they do not seem to have been a strain of bioform created by any of the Hive Fleets already known to have invaded Imperial space. It may be that they are the last survivors of a Tyranid reconnaissance of the galaxy before the arrival of Hive Fleet Behemoth. Even stranger, whilst the survival instincts of the other Genestealer strains leads them to flee the oncoming arrival of their parent Hive Fleets, Ymgarl Genestealers actively seek them out, as if hoping to once again hear the comforting presence of the Hive Mind. Jumping from planet to planet, they spread across the galaxy searching for worlds that lie in the path of an approaching Hive Fleet. Once there they will lay dormant until the Hive Mind reasserts contact with them and they can hunt alongside the rest of the Tyranid swarm. However, the Hive Mind has no desire to reabsorb their biomass or genetic legacies, lest their instability spread throughout all of the bioforms in the Hive Fleet. Once the target world has had all of its biomass devoured, the Ymgarl Genestealer brood is abandoned, forced once more to enter their hibernation. Unfortunately, human starships often investigate the Dead Worlds left in the wake of a Tyranid attack. In this way, they have come to learn more about the horrific xenos, amidst the forlorn hope of discovering survivors, or as scavengers come to pick over whatever wealth may remain. These fools and idealists eventually leave with a far more deadly cargo hidden within their holds, ready to spread the cycle of death and terror anew.

At first, Ymgarl Genestealers were not thought to be part of the broader Tyranid race, but were instead thought to be xenos native to the moons of Ymgarl. However, two-hundred standard years later, during the invasion of Hive Fleet Behemoth beginning in 745.M41, the Tyranids used Genestealers as shock troops and melee infantry in countless battles against the Imperium and the other intelligent races of the Milky Way Galaxy. The Magos Biologis of Mars spent many years trying to classify the Tyranid artefacts and bioforms left behind on Macragge after the invasion of Hive Fleet Behemoth was stopped by the sacrifices of the Ultramarines. Yet they could only learn so much of their origins from these remains. The only notable discovery was that the Tyranids used the Genestealers as their shock troops. It was believed that these xenos had spread across the galaxy on board Imperial cargo barges and derelict Space Hulks. Many of the Imperium's most violent encounters with Genestealers before the arrival of the Tyranids had been on board infested Space Hulks and names of such Hulks as the Sin of Damnation were forever synonymous with them. The presence of Genestealers among the Tyranid bio-forms proved that these previous assumptions concerning the Genestealers' independent origins had been false. Further genetic analysis confirmed that all Genestealers, even the Ymgarl variant, were Tyranid bioforms.

In response to this news, the Space Marines of the Salamanders Chapter unleashed a xenocidal campaign to purge the moons of Ymgarl of the foul creatures and the Inquisitors of the Ordo Xenos intensified their search for any signs of new Genestealer infestations, but little else could be done to deal with the problem. The question continuing to perplex Imperial savants is whether the Ymgarl strain of Genestealers are the remainders of an unknown ancient Hive Fleet that entered the galaxy before Behemoth, or whether there is more to the current Tyranid invasion that has yet to become apparent. Regardless of the outcome, the Ymgarl Genestealer strain was not completely destroyed by the Salamanders' efforts. They endure in the darkest corners of the galaxy, always waiting for the opportune moment to infest new worlds and offer another sacrifice for the Great Devourer. The truth about the Ymgarl strain has yet to be revealed.

Adrenal Genestealer

Adrenal Stealer - Hector Ortiz

Adrenal Genestealer

Adrenal Genestealers are a newer strain that have emerged within the Tyranid armies: deathly agile and relentless, these dangerous new foes spring out from every dark corner, unleashing volley after volley. Attached to these deadly creatures are Adrenal Glands, a common Tyranid Biomorph which can be found on most of their front-line fighters. Polyp-like organisms clamp themselves onto the host and secrete doses of a powerful adrenaline-like substance during combat, making the host creature relentless and nigh unstoppable in the heat of battle.

Vectori-Strain Genestealer

Vectori Strain Genestealer

Vectori-Strain Genestealer

The Vectori strain represents a classification of Genestealers adopted by the Deathwatch of the Jericho Reach to refer to the unique Genestealer breed encountered aboard the Space Hulk Mortis Thule. Much more agile than the purestrains from which all Genestealers derive, this xenos breed is well adapted to moving swiftly, as well as silently through confined spaces, while their lowered body mass reduces the energy required of their metabolisms, allowing them to operate effectively for longer periods without sustenance. Vectori Genestealers are nimble and stealthy hunters, operating with a focus and efficiency natural to such creatures for which economy of energy is an essential facet of survival. However, their lighter physiology makes them ill-suited for direct shock tactics, being not as durable as those of other purestrains.


Broodlord model space hulk

A Tyranid Broodlord

The Broodlord, or Corporaptor Primus, is the ultimate product of Genestealer evolution. The Broodlord is immensely strong, agile and durable, which makes it a superb frontline warrior. In addition to their already potent combat abilities, the Broodlord also has a few Tyranid Biomorphs or biomechanical weapon-symbiotes to chose from beyond just its standard rending claws and scythe-like talons.

Broodlords act as commander for Tyranid assault forces, personally leading attacks. They bear the "synapse" ability frequently observed in higher forms of Tyranids, which allow them to coordinate the Hive Mind's psychic commands over less-intelligent Tyranid species. This is unlike the traditional Genestealer Cults which grow and rise in infested Imperial worlds to take its followers from among the local populace, and psychically dominate them and be worshiped as gods. The army led by the Broodlord is an infiltrating vanguard operating in a similar manner to the Tyranid Lictor. A Broodlord at the heart of a telepathic link can track its foes with the senses of many and employs its greater intellect to coordinate and command the lesser Genestealers.

Vectori-Strain Broodlord

The circumstances that lead to a Broodlord coming into being are still relatively unknown to the Ordo Xenos, but speculation and theories abound on the subject. In the case of those found aboard the Space Hulk Mortis Thule in the Jericho Reach, it has been theorised that exposure to the energies of the Warp and isolation from the Hive Mind has somehow culminated in the creation of an "alpha" Genestealer, a creature of terrible majesty and dreadful might that exists at the heart of the collective brood-mind shared by any given group of Genestealers. Whatever the truth of their origins, Vectori Broodlords are the most frightening of these creatures. Connected psychically to an instinctive network of hunters, they lie in wait while their lesser brood herd unwitting prey into traps and ambushes orchestrated by a being of vicious cunning and inhuman intellect. When they choose to act directly, very few combatants can endure their onslaught.

Vectori-strain Genestealers have a constant telepathic link with each other which can function clearly and without restriction (such as from intervening objects or other forms of shielding) up to one kilometre. This allows them to communicate with one another and pass information to nearby Genestealers swiftly and surreptitiously.

Genestealer Cults


A Genestealer Cult on the rampage

Genestealer Cult is a xenos-worshipping secret society made up of and controlled by Genestealers that thrives in the dark, dank corners the Imperium. Secretive, stealthy, and utterly malignant, Genestealer Cults are the cankers growing unseen in the hidden spaces of Mankind's realm. Some cultists are truly monstrous, skulking along dank tunnels with robes or hessian sacks covering their xenos anatomies. Others are merely pallid and bald, able to pass for loyal Imperial citizens whilst their wyrm-form tattoos remain hidden. These latter-generation brethren mingle amongst the herd of Mankind like wolves in sheep's clothing, working so hard amongst the crumbling machineries of Human industry that none spare them a second glance -- but under their work fatigues and rough miner's apparel, they all bear the mark of the alien.

Ordo Xenos Data

Ordo Xenos Departmento Analyticus Record
Designation Genestealer
Common Title Stealer, Leech, Sewerstalker, Scuttler, Clawfiend, Ghost
Species Name Corporaptor hominis (Purestrain Genestealer), Corporaptor ymgarli (Ymgarl Genestealer) , Vermis (Tyrannus) Furii (Broodlord)
Average Height 1.9 metres
Average Weight 0.3 tonnes
First Encountered Moons of Ymgarl
Role Infiltration
Threat Evaluation High


Genestealers appeared in the 1st Edition of Warhammer 40,000 (Rogue Trader), but at the time were not a Tyranid species. They were simply noted as being an "enigmatic monster ... from one of the moons of Ymgarl", now "spread throughout space" and "threatening to become a real menace". Since then it has been revealed that they were the advance forces of the Tyranid invasion and are now often seen as part of a Tyranid army.

The Genestealer Cult is a substitute army that has been introduced several times for Warhammer 40,000. The initial introduction by Paul Murphy, Bryan Ansell, and Nigel Stillman was printed in White Dwarf issues 114-116 (1989). This was followed by an article from Andy Chambers and Jervis Johnson in White Dwarf issue 145 (1992) that detailed the Genestealer Cult as part of a Tyranid army. Later, Tim Huckelbery detailed the Genestealer Cult army in issues 40 and 41 (1999) of the Citadel Journal, under the title Codex: Genestealer Cults. This official supplemental Codex provided official rules for using Patriarchs, Magi, Hybrids and Broodbrother units. It even included rules for a "Transport Coven Limousine." Later, in the first Codex Tyranids, these rules were incorporated as the "Genestealer Cult Army List" and included all of the characters in their previous form sans Limousine.

In the Tyranids Codex for the 3rd Edition of Warhammer 40,000, there were no rules provided for the Genestealer Cults. With the introduction of the Broodlord in the 4th Edition, Genestealers could once again be fielded as their own army, albeit one that was restricted to HQ and Troops units only (which arguably makes it quiet ineffective). Before the 4th Edition, the 3rd Edition Genestealers were the oldest models in use to date (they were the same ones from Rogue Trader and the Space Hulk game).

There are currently two variants of the standard purestrain Genestealer: the Broodlord and the baseline Genestealer. In earlier incarnations of the Warhammer 40,000 universe, there were five separate types of Genestealers, representing the Genestealer Cult variant army, including: Genestealer Patriarchs, the Genestealer Magus, standard Genestealers, Genestealer Hybrids, and Brood Brothers.

Genestealer is also the name for the second expansion produced for the Games Workshop tabletop miniature wargame Space Hulk. The expansion is named after the Genestealers that the Space Marines battle as the primary adversaries of the game. It features psyker rules for Space Hulk.