11th Black Crusade

In 301.M39, Abaddon the Despoiler launches his 11th Black Crusade against the Orks of WAAAGH! Murgor. The Despoiler's fleet had become lost in the Warp, finally returning to realspace in the path of the greenskin horde. In the ruins of Relorria, the Black Legion brought the Orks to battle, Bolter rounds and Chainswords tearing into the green-skinned xenos. After months of bloody warfare, Abaddon decides to leave Relorria to its fate and the Black Legion returns to the Eye of Terror -- but not before the Warmaster of Chaos fills the holds of his fleet with captured Orkoid specimens.

History
At the outset of the Eleventh Black Crusade, Abaddon bound a Daemon of Tzeentch within the oculus of his vessel, hoping to find a path through the tumultuous Warp Storms around the Eye of Terror. Tormented with impossible riddles and twisting falsehoods, the Daemon was driven completely insane, leading Abaddon thousands of light years off course. Writhing, the Daemon tore itself in a vortex of madness, bending time and space around the fleet. Abaddon's ships were scattered across the void of realspace. Undaunted by the failure of his daemonic navigator, the Warmaster loosed his Black Legion upon the nearest planet, the cardinal world of Relorria. Descending on Relorria, the Traitors encountered a rival for their prize – an Ork WAAAGH! led by Murgor “Undred Teef.” In a vicious and chaotic three-sided war, Daemons and Orks ripped each other apart in the burning ruins of Relorria's vast Reflecting Towers.

Abaddon used this chance encounter with the Orks to conduct unspeakable experiments with Daemons and alien creatures, attempting to fuse the material and the immaterial together into some new manner of horror. Fascinated by the psychic link between the Orks and their instinctive use of Warp energy, the Warmaster took thousands of the xenos back with him to the Eye of Terror to continue his research. The Black Legion eventually retreated from Relorria, leaving the battered survivors of Humantiy to destruction at the hands of the Orks.