Sired by the Daemon Bel'akor on an unsuspecting woman, the man who would become Archaon began life as Diederick, and was in fact a warrior dedicated to Sigmar. For some time he fought for the Empire of Man and was a renowned Templar. But one day, he learned of the prophecy of the Everchosen, Chaos' greatest champion fated to bring about the end of the world. To his horror, Diederick learned that he was the one the prophecy spoke of. Desperate for salvation, he sought guidance from his god Sigmar. But Sigmar was silent. Despairing, Diederick concluded that his destiny was inevitable.
Many years (and many dead bodies) later, and Diederick the warrior of Sigmar was gone forever. In his place was the merciless Archaon the Everchosen, determined to fulfill the Chaos God's will even as he secretly hates them as much as he does any other god, resenting the fact that all his life he has been a pawn in their games.