Dominion Zephon, the Bringer of Sorrow, was a member of the Crusader Host from the Blood Angels Legion along with his Legionary Brother Marcus. He was sent to the Crusader Host due to the failure of bionics replacing his lower arms and legs to work at an efficient fighting level. Although others were imprisoned, he was allowed some freedom to continue his duty marking the names of the dead.
Before becoming a Legionary, he was a member of a tribe and learned to play the harp. Like other Blood Angels, he was both a warrior and an artist. However, the attack that removed his ability to fight also stole his ability to play music. Both his arms where severed below the elbow and both his legs were mutilated by a alien blade. Both arms where replaced by augmetics and his left thigh and knee, as well as his right foot with a four taloned claw. Nine surgeries were unable to replace his ability due to his body rejecting augmentations. He still attempted to play music and to fight, but he could only fire a boltgun every fifth time he attempted due to his nerves not responding, and his aim was limited due to his nerves misfiring and causing him to tremble.
After the Horus Heresy began and the Blood Angels disappeared, he pleaded with Malcador the Sigillite to be allowed to search for them, but he was denied on 13 different occasions. During the War Within the Webway, as the Emperor's forces were pushed back to the Impossible City, the Custodian Diocletian recruited him for their plan of reinforcement on recommendation by the Sigillite. Although Zephon tried to demonstrate that he was unfit to fight, he was required to attend with the Custodian anyway.
Following the Webway War, Zephon began spending much time in the Imperial Palace with fellow veteran Arkhan Land. When the Blood Angels under Sanguinius arrived on Terra, Zephon wept and Land agreed to help repair Zephon's bionic limbs. Land discovered that the limbs would always be rejected by Zephon's body, so to bypass this implanted fragments of a acquired Dark Age of Technology-era Artificial Intelligence into his arm and head. He used the limited AI to trick Zephon's body into accepting the new limbs, and in exchange Zephon agreed to take Land before Sanguinius.