Legend holds that at the beginning there was only Anu and from his epic struggle came all of creation... or has the truth really been lost with none willing to correct it...

Two angels loved each other in secret for a vast millennia. When they cast aside their wings to become mortals, it was a year after the Worldstone was destroyed. Two years later, after the birth of their daughter, Imperius catches wind of it. And he is not amused. Yet, to him, the child shows promise. -Based on Post Diablo 2 content, Diablo 3 content and through Reaper of Souls-

It would take one of the seven demon princes to corrupt the holy Standard Bearer Michael and it would take Asmodeus himself, the demon prince of lust, to make him enjoy it. Asmodeus/Michael.