Daemon

In a wold where selling your soul to a higher being like an angel or a demon is seen as a sensible but desperate move, you decide you can't take it any more. On your way to an auction house to sign your life away you meet him. In alll his archdemon glory. He offers you a deal ' He won't take your soul if you can guess his true name in a month you serve him, if you don't guess it you are his ethernal servant, if you do? Well he's forever yours. For now he lets you call him Daemon.