I don't think he could have worked his way out of hell. He is still quite evil, and escaping hell on your own merits involves becoming good. Of course, he could also have made a deal with a devil and convinced him that he is more useful to their cause in the Netherworld. Maybe someone who is skilled at drawing souls together and binding them into weapons would also have the skill to navigate his own soul straight into the netherworld before a demon could come and collect it though. Where is Gastrius now? Or any of Kyorlin's other unaccounted for students? What can you tell us about the Demon Lords from the Lord of the Balors scenario? Where they all (excluding Hyborem) originally mortals, or were some created as demons to begin with, or even as angels? What gods did they serve? What gods, if any, did they choose to serve once becoming demon lords?