I finally finished off my first overlord. 7 levels below me, which apparently means no XP. Sad face. Also used up every single mana scroll and potion that I had. I had to finish him off with fire touch. So yes, I just punched out the evil overlord. This doesn't have much to do with Q & A, I just wanted to share it.
Oh wait, here's a question. Will NPCs actually celebrate when you win? Right now I notice they've just gone from moping about evil overlord X to moping about evil overlord Y. Don't get up, people, don't worry, I just punched out a dragon, I'll just go on to the next thing right away. Don't bother to thank me.