The Unity was a warship in the Imperial Fists Legion during the Horus Heresy. It was part of the Retribution Fleet sent by the Primarch Rogal Dorn to confront Horus when the Heresy began. However, due to severe Warp Storms, the Fleet was left stranded in the Phall System and the Unity later fought the Iron Warriors Legion, in the Battle of Phall. During the battle it worked together with the Imperial Fists' warships the Halcyon and Truth, to destroy the Iron Warriors Battle Cruiser Dominator; however as they turned away from its wreckage they came under attack from the Gloriana Class Battleship Iron Blood. The Iron Blood was commanded by the Primarch Perturabo and such was its level of firepower, that its attack completely destroyed the Unity.