A Genestealers is a species of @Tyranids used as the ultimate shock trooper. Their purpose is to advance ahead of a Hive Fleet and pinpoint potential planets for the Tyranids to devour. They are amongst the deadliest creatures in the Galaxy, combining high cunning and lightning-fast reactions and movement, with large, extremely sharp claws that can rip through the toughest armour in seconds.
Possibly the most terrifying aspect of Genestealers is their insidious method of reproduction. Genestealers reproduce completely separate from a Hive Fleet, unlike the majority of other Tyranid creatures. Through the use of a tube-like tongue called an Ovipositor, known informally as the Genestealer's Kiss,they insert a tiny embryonic organism containing their own genetic material into a host victim. Over time this organism alters the host's genetic code, and their consciousness is also completely suppressed by a localised version of the Hive Mind, known as the Brood Mind, becoming a virtual slave. Any offspring born by the host will be horrific Genestealer Hybrids, which the host will be psychically mesmerised to care for, giving rise to the @Genestealer Cults that grow in secret within human and other societies.
Genestealers have an interlinking telepathy similar to the greater Hive Mind which is generated by the entire Tyranid race. This Brood Mind is smaller and more localised than the Hive Mind and is used to exert complete control over their host victims[3] and also for communication.[6] Their telepathic link with each other can function clearly and without restriction (such as from intervening objects or other forms of shielding) up to one kilometre.[8] It also acts as a psychic beacon to draw a Hive Fleet towards the infestation in order to devour the planet.
A @Genestealer Cults is a community of Genestealers, genestealer hybrids, as well as the completely human convert-hosts, infected victims and genetic relatives known as Brood Brothers, existing within the society of a species Tyranids view as prey.
Genestealer cults form if a Genestealer infects members of another species with its genetic code. The resultant changes in the genome of the host cause a fanatical loyalty to the genestealers, as well as a drastic change to their reproductive system; their firstborn children will be hybrids, a grotesque mixture of the host's race and genestealers. These hybrids infect further victims, and the infection spreads exponentially. Fourth generation hybrids produce purestrain genestealers, and the cycle starts once again. This brood of purestrains, hybrids, and neophytes is held together by strong psychic and genetic bonds, and assembles around the original genestealer, which becomes the patriarch. Because this community is often hidden behind the facade of a religion or political movement, it is called a genestealer cult by the Imperium.
As the cult's numbers grow, more specialized types of hybrids are created to serve the patriarch, which is now worshiped as a god. These include magi, primuses, loci, etc.. The cult will often grow and plot below the surface of their host world, using this base of operations to gradually infiltrate into the above society. Later generations are less monstrous than their forbears and can freely walk among Imperial society without much notice. Often a genestealer cult will recruit from the downtrodden underbelly of society, characterizing themselves as liberators from the brutal yoke of Imperial rule. A fully mature cult can be huge, numbering in the billions and covering several worlds.[14a]
The Cult's primary concern is their propagation, but over time this transitions to preparing their host world for the coming of a Tyranid Hive Fleet. Cultists often see this as an anointed holy day of salvation, and they will work fanatically to see a victim population is ready for consumption. At the chosen hour the Genestealer Cult rises up, unleashing a devastating and well-planned assault that can devastate entire Systems