Formerly the duke of Gwent, he stole the British throne from King Constantine while the latter was conquering Rome. Constantine sent one of his generals, Trahern, to deal with Octavius, and Octavius was forced to flee to Norway. He put a contract on Trahernís life and, when Trahern was assassinated, he returned to Britain to rule until he died. He was succeeded by Maximus.
He is to be identified with Evdaf.