The Heavy Crossbow of Umbar (x7) (+18,+18)
+3 strength, constitution, shooting power. Provides resistance to lightning, light, dark, blindness. Cannot be harmed by acid, electricity, fire, cold. Aggravates creatures nearby.
When aimed, it fires a magical arrow with damage 150. Takes 21 to 40 turns to recharge.
Min Level 60, Max Level 127, Generation chance 5, 20.0 lbs

(Angband 3.1.2v2)