The Harrowing was a Chaos Space Marine warband in the early years of M33. It was led by the warlord Gzrel and a coterie of Chaos Sorcerers comprised of Maroth, Xiatsis, Cottadaron and one called Horkos, who was apparently weakest and most subservient to Gzrel and Maroth. The warband had over a hundred renegade Astartes members, as well as enginseers, mutants and slaves. It controlled the ailing hunter ship, the Blood Crescent, and used it as a mobile base of operations.