Such beautiful animation and spritework! I LOVE it! The core loop is very simple and appears to have some really cool interactions you can have with it. Well done :)
The werewolf and imps felt a little too tame in variations on enemies. I would have loved to see something that moved differently, like a guy that moved twice, or a flying unit that ignored unit collision. I think the pace was a little slow for my liking for a game jam. I think you could have gotten away with one level per new summon and had people asking for more instead of (probably only me) thinking there was a bit too much. Sorry, that's a weird gripe for a jam. :P
The need to escape after the chaos you cause was a bit frustrating at first, but adds a bit deal more threat to the situation. One strategy might be to overwhelm but then you might have a tough time escaping. It'd be especially fiendish to make the door spawn under where the enemy died lol.
Great work on this! Excellent entry!