During the Horus Heresy elements of the Raven Guard Legion, under the command of Branne Nev and the Imperial Army's Therion Cohort led an invasion of a Traitor controlled world the name of which has long been forgotten. The planet's second capital city of Milvian was assaulted in force by the Therion Cohort, led by brothers Marcus Valerius and Antonius Valerius, in which both brothers led their battle groups with their own Capital Imperialis'. During the battle Marcus' Capital Imperialis took on an enemy Warlord-class Titan, and despite a Warp Missile detonating within the transport's Void Shields the mighty vehicle was able to continue fighting to the end of the campaign and further into the Horus Heresy.