A Genestealer Hybrid is a mixture of a Genestealer and another race. Hybrids are the progeny of humans (or other races) infected by Genestealer genetic material.
Purestrain Genestealers can only reproduce by infecting a victim with their genetic material. The gene-host survives as a healthy human being, but, upon becoming a parent, the gene-host's firstborn child is indelibly marked by the gene-infection. Once the child matures into a Human-Genestealer Hybrid, it can pass the infection on to other Humans, whose firstborn will also be born as Hybrids. It is only the firstborn child of infected parents that is a Human-Genestealer Hybrid; later offspring will always be normal humans.
The first generation Hybrids closely resemble Purestrain Genestealers. But, with each new generation of Hybrids, Genestealer traits give way to Human traits, until fourth generation Hybrids are all but indistinguishable from untainted Humans. However, a Hybrid will always display the Genestealer's primal instincts; these always remain in their genetic structure, and - no matter how Human in appearance - a Hybrid belongs to the Genestealer brood.
Purestrain Genestealers are totally incapable of passing as Human. Their multiple arms, bulbous heads, glaring eyes, and animal crouch give them away; no amount of clothing and make-up can disguise such characteristics. However, later generations, particularly the third and fourth, become more humanoid in appearance. Indeed, many Genestealers of advanced generations can appear as Humans at first glance, especially if wearing concealing clothing. However, as their sharp teeth and hypnotic eyes are somewhat of a giveaway, they tend to avoid speaking to strangers or looking at people straight in the face.
It follows that, in many ways, the later generation Hybrids are the most dangerous - they can move freely among Humans, passing on their terrible disease unnoticed.
Due to the sheer number of Humans throughout the galaxy they are the race most commonly affected by Genestealers. Nevertheless, there is no reason why any other race cannot be infected; Ork-Genestealer Hybrids are perfectly possible - indeed many exist. The appearance of such Hybrids would, of course, depend on the parent race, and they would show different physical characteristics than a Human-Genestealer crossbreed.
Each hybrid generation possesses a somewhat specific anatomy. By infecting a victim with its genetic material, a Genestealer passes on some of its physical characteristics to the victim's first offspring. In the first generation, this gives rise to a Hybrid with a number of Genestealer traits. Through successive generations of Hybrids these traits become less extreme, until in the fourth generation the Hybrids can pass as normal Humans.
- First generation: The first generation Hybrids are born to human (or otherwise) parents, one of which has been infected. Of all the generations they resemble Genestealers most closely. They have either three or four arms.
- Second generation: Second generation hybrids always possess three arms, one of which ends in the genestealer claw.
- Third Generation: These hybrids possess bodies somewhere between the crouched bodies of genestealers and the humanoid shapes of humans. They appear perpetually crouched, possess two or three arms one of which might end in a genestealer claw. Some lack the ovipositor of preceding generations; these are called drones or neuters, although they can still infect other races through their blood.
- Fourth Generation: This generation is virtually indistinguishable from members of the host species. They retain the hypnotic gaze of genestealers, making them rather charismatic. A "mutant" which can appear among this generation is the Magus, which takes the highest position in a Genestealer Cult, besides the Genestealer Patriarch. The first offspring of fourth generation hybrids are invariably purestrain genestealers, allowing the cycle to continue.
Purestrain Genestealers and first and second generation Hybrids have no psychic powers except for their innate abilities, Hypnotic Gaze and Brood Telepathy. Third and fourth generation Hybrids, however, will often have additional psychic powers. Inherited psychic traits passed on from infected psykers in the Hybrid's ancestry may become apparent in the near-human third and fourth generation Hybrids.
Purestrains and Hybrids can recognise human psykers when they find them. Genestealers are attracted to psykers, and share none of the normal human's prejudices against them, simply regarding them as exceptionally advanced specimens of the race. Consequently, the psykers in a community are among the first to be infected by the Stealer gene. This means that Human psychic traits will pass into the gene pool of the Hybrid brood, to be inherited by later generations. Thus, by the third and fourth generations, the Hybrids can develop full psychic powers in addition to possessing the two innate abilities of Genestealers.
Psychic Hybrids tap raw psychic energy emanating from the primitive Genestealer Power that exists in the warp - the shadow image of the Genestealer species' will to survive. Psychic Hybrids who worship a Chaos Power may of course draw psychic energy from their patron, thus tainting their simple Genestealer souls.
Although most documented cases of Genestealer Hybrids have been of human hosts, Genestealers can infect a range of different species. The taint created by Genestealers is known to be able to be sown amongst almost every race with the likes of the Tau, Eldar, Hrud and Orks being species that can spawn hybrids with the contagii being an adaptable breed.6
Eldar biology is noted being less crude compared to Humans with the Genestealer taint taking many generations before producing a primacii mutation. By the time this is discovered, the vigilant Eldar manage to eliminate the hybrid community which is quickly discovered and destroyed.6
Orks are not an ideal species for Genestealer infiltration, although sometimes 'stealers will infect Orks if no better host species is available. Generally Genestealer-Ork groups are only sucessful when a community of Feral Orks is infected, as more "civilised" Orks are usually able to instinctively detect the presense of alien contamination and will doubtless wipe out the infected Orks.3p26
Numerous miniatures appeared for hybrids of the later generations and most depended on arm and weapons sprues of the Imperial Guard. Besides, for a short time available miniatures for mounted hybrids needed individual parts of mounted imperial soldiers. Beside these metal miniatures plastic models which owned own arm sprues also appeared, in the Space Hulk extension Genestealer. These were also included in the game Tyranid Attack and in the box Terminators and Tyranids. Also, individual parts were brought out for Inquisitor game to convert hybrids and a Magus.