A Champion is anyone who was blessed with powers bestowed by a god.
Gods may only have one Champion each, as each one is a sort of vessel for their power on earth. They hold this power until their death, and such is unexchangeable until the Champion's soul is released from their body alongside it. Thus, the gods have to particularly careful and certain when picking a champion, a fact which leads to plenty of them refraining from ever assigning their abilities to mortals.