Black Hat definitely fits into the troll clause! In other words you can bring him into Ryslig as is -- provided his non-human attributes pose no advantage. In other words, his super sharp teeth can't actually be super sharp, although they're free to LOOK sharp.

If you choose to bring him in as a human, he can develop his canon attributes along with the monster traits. Again, these canon traits can't actually pose any advantage. They also can't conflict with his monster traits, e.g. if he becomes a Nymph, he'll still need green skin.

We look forward to your application!