The Iron Crown of Beruthiel [0,+20]
Heavily cursed. -5 strength, dexterity, constitution. Cannot be harmed by acid, electricity, fire, cold. Prevents paralysis. Grants telepathy. Grants the ability to see invisible things.
Min Level 40, Max Level 100, Generation chance 8, 2.0 lbs

(Angband 3.1.2v2)