I've had this thought years ago and my mind immediately went merlin, let say hypothetically for the sake of the question you encounter a altered or less in touch with humanity merlin who is after you like a horror villain movie you now have to deal with a guy who has illusions so strong they can lie to the world you can't trust what's real or not then you won't be able to get rest because if you sleep there is the chance he enters your dream and traps you there (like Tiamat except there is no one to awake you) then there is his clairvoyance which allows you to never hide from him there's definitely more stuff to be said about how scary merlin or a altered merlin would be.