The boss rattle bones drops Myth Fairy. I also know that he drops mounts like a hoarse, broom or wings for one day only. For clothes he drops stormweved shoes.
Lady Black hope drops mounts for a day, a unicorn statue and pets. The pets include a imp and I think maybe a myth sprite. She also drops a novice robe.
lord night shade drops a blue banshee, and some holiday items.
Sergant Skullsplitter in unicorn way drops amyth fairy.