For a short adventure / one-shot, I played an intelligence-based tome warlock (using some of the play test materials). His patron was… himself, in the past. He was a terrible evil wizard who realized the error of his ways, wiped his own memory, and restarted. His tome was just his old spell book, most of which was pretty gnarly stuff. Slowly finding that out would have been a fun journey if he was a long-term character.