Show him the Crown of Bone for a one time bonus of 2,850,000xp.
Lore & Dialog
Warden tells you, "Northeast of Shoushi lays an ancient Empyrean castle ruled by the Baron Nuvillus, now a living skeleton."
Warden tells you, "Atop his head the Baron Nuvillus wears a Crown of Bone."
Warden tells you, "The castle is located at 24.2S, 76.8E."
Warden tells you, "Go there, obtain the Crown of Bone and return to me with it for a reward."