The Mace 'Taratol' (3d4) (+12,+12)
Slay Xdragon
Lightning Brand
Immunity to Lightning
Activates for haste self (20+d20 turns) every 100+d100 turns
Level 20, Rarity 15, 20.0 lbs, 50000 Gold

(Hengband 1.6.0)