The Origins of Serath are very simplistic. He was born of an Angel and a Demon. He was the eleventh and last born. Born at the same time as Galdrei and Baalcifer. He was the perfect balance of evil and good. People feared though that he would tip the balance of good and evil he hadnt chose what path to follow. So Baalcifer and Galdrei both lead clandestine actions to make humans seal away Serath for all eternity or so they hoped.