Lanimayesh was an Eldar Craftworld, whose population was destroyed after it was invaded by the forces of Khorne. The aftermath of the massacre left Lanimayesh silent and adrift for many years, until it slowly became corrupted by the Warp, as the barrier between the two realms began to thin on the Craftworld. Once Khorne learned of this, he sought to permanently claim Lanimayesh and make it a shrine to the massacre that claimed the lives of the Eldar, that once made it their home. However, the Seers of Biel-Tan received a vision of Lanimayesh's plight and saw that it would set events into motion that would lead to their own Craftworld's downfall, if Khorne succeeded.
Acting quickly, a strike force led by Farseer Tyleannar arrived on the Craftworld through a Webway Portal and sought out Lanimayesh's psychic matrix. By then, the servants of Khorne had already begun breaking through the Craftworld's thinning barrier and attacked the strike force as it made its way to the heart of Lanimayesh. Though they were outnumbered, the Eldar of Biel-Tan fought their way through the Daemons and once they reached their goal, Tyleannar acted quickly to awaken Lanimayesh's dormant psychic matrix, while the strike force fought off the increasing number of Khorne's servants that were materializing on the Craftworld. Once the matrix was awoken, it was alerted to what was about to befall it and began gathering its remaining energy into Lanimayesh's Webway Gates; which slowly engulfed the Craftworld with the power of the Warp. With his task complete, Tyleannar opened up a Webway Portal and the survivors of the strike force escaped back to Biel-Tan, just before Lanimayesh was torn asunder, as it fell into the Realm of Chaos.