That's a tough one, there's so many good choices... [Seriously giving the question some thought.] Tentacles are a classic for a reason, you can't really go wrong with those... One of my favorite partners at home had a snake tail, wings, fangs, and claws.

Oh, it always helps if they're bigger than me.

[The Demon King is a noticeably tall man, and Evangeline very much appreciates that.]