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 e