Fantastic art, music, and sound! Really loved the concept as well - I think playing as a boss's servant or minion is a great idea, and I'd love to see it developed further. Being able to harm or heal the wrong target also adds a nice element of challenge that additional bosses or heroes could tap into with different movement patterns.
As others have mentioned, you can become stuck in the floor - but hilariously enough, I was still able to catch and throw blocks where I'd been wedged. So with just the top half of my skull sticking out of the floor, I managed to defeat the hero! Had a good chuckle after that!
Great game!