Teus Sullus was a Captain of the Ultramarines during the Great Crusade and Horus Heresy. An old veteran commanding the 39th Company, Sullus survived the treachery of the Word Bearers in the Battle of Calth and was part of a force of survivors under Remus Ventanus. Sullus was goaded into killing Word Bearers commander Morpal Cxir during the battle, which allowed the Daemon Samus to enter the Materium. Trying to make up for his outburst, Sullus attempted to slay the Daemon but was badly damaged in the process. Sullus survived, and though crippled took part in a final defense against a counterattack by Foedrall Fell.