Genestealer - Ymgarl Genestealer: Imperial researchers of the Adeptus Mechanicus conjectured that the Ymgarl Genestealer was a form of the species that separated from the main conglomerate of the Tyranids' Hive Fleet Behemoth or some other early reconnaissance force of the Hive Mind several hundred Terran years ago and, having completely lost its psychic link to the 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 their colour like a chameleon, so as to blend into their surroundings and remain unseen until they strike or flee.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, utilising 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, an 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 possessed of fresh blood passes near enough to disturb their dreamless sleep.The origins of the Ymgarl Genestealers remain a mystery to Imperial scholars, 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 these 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 species, 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 in 745.M41, the Tyranids used Genestealers as shock troops and melee infantry in countless battles against the Imperium and the other intelligent peoples of the galaxy.The magi biologis of Mars spent many Terran 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 main Tyranid hive fleets 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 scholars is whether the Ymgarl strain of Genestealers are the remainders of an unknown ancient hive fleet that entered the galaxy before the 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 full truth about the Ymgarl strain has yet to be revealed.