The Jewel 'Evenstar'
Provides resistance to cold, dark, nether. Cannot be harmed by acid, electricity, fire, cold. Sustains intelligence, wisdom, constitution. Sustains your life force.
When activated, it restores your experience to full. Takes 150 turns to recharge.
Min Level 40, Max Level 100, Generation chance 2, 0.3 lbs

(Angband 3.1.2v2)