"The greatest threat is ever the one we know least about, and few xeno-forms epitomise this notion more than the Lacrymole. Their greatest knack, its seems, is convincing us that they no longer exist."
- — Lord Inquisitor Parnival Grundvald in an address to the Betacairn Conclave
The Lacrymole were a sentient xenos species present in the Milky Way Galaxy that were driven to near extinction by the Emperor and the Space Marine Legions during the Great Crusade in the 31st Millennium, though the survivors of that purge have preyed upon Imperial citizens for millennia afterwards.
During the Horus Heresy, a Lacrymole was used at least once as an assassin by the forces of the Warmaster Horus. This particular Lacrymole was able to assume the form of a warrior of the Legio Custodes and infiltrate the planet Bastion where it was to assassinate the senators and nobles of that world's ruling class, an act that would have led the planet to revolt against the Imperium and side with Horus. In later times the existence of the species only became fully known to the Inquisition after they were discovered by the Inquisitor Grundvald on the world of Betacairn. When he discovered the existence of such a horrific alien species, Grundvald called an assembly of the Inquisition's Ordo Xenos and had the Lacrymole declared to be Xenos Horrificus, an Imperial designation requiring that every member of this alien species be exterminated upon discovery.
A notable encounter is the Charnel Spectre incident, or the Lacrymole Encounter as it is sometimes known, which occurred during the early days of the Achilus Crusade before the death of Warmaster Achilus and before the true extent of the Imperium's foes had been uncovered. As the Crusade fortified the regions around the Well of Night, countless scouts ranged out in all directions. Assessing new worlds for conquest and spying on heretical populations and blasphemous alien empires they sent information streaming back to the Warmaster. Among these reports was the appearance of an ancient Space Hulk -- the Charnel Spectre. The Charnel Spectre was an item of interest to the Inquisition as it had been sighted centuries before and records spoke of it containing the remnants of a relic ship of the Great Crusade; a ship which might have once belonged to the fledgling Inquisition.
A mission was organised; and led by Inquisitor Malas Dyce of the Ordo Xenos and supported by a Deathwatch Kill-team it set off to find the Space Hulk's location. After months of false leads Dyce and his team finally tracked the Charnel Spectre, following its erratic wake in the Warp, to the edge of the cursed Credence system just beyond the boundaries of the Iron Collar. There they boarded the vessel and began their search for the relic ship. What they encountered instead was a nest of xenos which had apparently been living on the Space Hulk and using it as a base for centuries. At first the Kill-team thought they might be facing a Genestealer infestation (common on such ancient space hulks) as clawed shapes moved in the shadows and hissing sounds were heard echoing down the corridors. It was not until it was almost too late that they realised the aliens were shape-shifters.
Laying deadly traps for the Kill-team the aliens had some of their number appear as vile alien beasts, or clawed horrors like the Genestealer, and drew the Battle-Brothers, the Inquisitor and his Acolytes into a hunt. Only then would others pick off lone members of the group from behind (the Acolytes first among these) and assume their forms, then get close enough to strike with surprise. After only a few hours of entering the Space Hulk, only Dyce and a few Battle-Brothers remained, and the Battle-Brothers were deeply suspicious that Dyce was an alien imposter. To save himself and return his report, the Inquisitor slipped away from the Kill-team during a firefight and made good his escape from the Charnel Spectre, leaving all of his companions behind. Upon his return Dyce was convinced the aliens encountered on the Spectre were the fabled Lacrymole, claiming they were one in the same with those creatures slain by Inquisitor Grundvald and thought put to rest. With no proof however, and the loss of a Kill-team he was derided by his peers and ended his career as a broken and babbling old man whispering of aliens in the dark.
The Lacrymole are vampiric shapeshifters, capable of changing their form at will after feeding on the blood of an individual. These aliens often stow away aboard Imperial spacecraft in human form so that they might feed upon the vessel's crew and passengers as they travel across the galaxy seeking out new worlds to feed upon. The Lacrymole's true form is that of a mass of flesh and limbs in constant motion, with only its black eyes remaining unchanged.
- Deathwatch: Mark of the Xenos (RPG), pp. 66-67
- Inquisitor (Specialty Game), pp. 144-145
- Forgotten Sons (Novel), by Nick Kyme