Complex sentence: Conan once seeks out a wizard he claims "Grey Wolf of Xanthus" told him about; he also mentions that he once knew a firebird, and claims that he ate him (saying that as joke).
Split into simpler sentences: Conan once seeks out a wizard he claims "Grey Wolf of Xanthus" told him about. He also mentions that he once knew a firebird, and claims that he ate him (saying that as joke).