|This article is about the Chaos Space Marine warband; for the Short Story by Rob Sanders, see The Harrowing (Short Story).|
They used high numbers of Chaos Spawn and their Chaos Space Marines were highly aggressive, or highly mutated (sometimes both). The warband occupied a decrepit warship called the Blood Crescent, which attacked and boarded the larger Titan Child in order to expand, garrisoned by members of a Renegade Space Marine Chapter. The Harrowing were victorious, though their first boarding wave suffered significant losses.[1x]
The fall of the warband occurred shortly thereafter, when a ship came out of the warp soon after they had taken the Titan Child. The unknown ship then sent an emissary to speak with Lord Gzrel: a former Thousand Sons sorcerer named Tolbek, accompanied by two Rubricae bodyguards, Helio Isidorus and Mabius Ro. Tolbek was searching for his former brother, Ahzek Ahriman. The name meant nothing to Gzrel, who offered the services of his other sorcerers, but Tolbek rejected them all.[Needs Citation]
Just before leaving, Tolbek realised that one of these sorcerers, "Horkos," was Ahriman in disguise. He asked Ahriman to come with him, but after Ahirman refused, Tolbek attacked him with the aid of the Rubric Marines and the Harrowing present in the room. Ahriman slaughtered them all with the exception of Gzrel's High Magister, Maroth. Ahriman then fled and released the survivors or the renegade Space Marine Chapter and, with their aid, retook the Titan Child and fled the sector, leaving the Harrowing leaderless in the Blood Crescent and left to face the unknown ship by themselves.