I have one character who got all the way up toward level 20, and then due to circumstances, was knocked all the way back down to 1. Essentially, he had to give up almost all of his life essence to seal away a terrible evil... had he given ALL of it, he might have defeated his enemy permanently, but he wasn't able to bring himself to do that. He's since had a Modify Memory type spell used on him so he doesn't remember anything of his previous self, because the information he'd learned could be used to unseal the being he had to deal with. All he knows is that he has a giant blank spot in his memory that he shouldn't be chasing after, and a weapon he didn't have before that he needs to protect with his life.