This could be an interesting idea. Maybe make a race against time boss. Like there's a Thrall that's about to be evolved into an Ogre the likes of which we've never seen, and it's up to us to prevent that from happening. Like there's a Thrall with Wizards linked to it to evolve it, and we have to kill the Thrall before it becomes and Ogre, and killing Wizards increases the timer. Could be interesting.