The Soul Cutter (3.5e Equipment)
From D&D Wiki
The Soul Cutter: The Soul Cutter is a blade bound to the soul of the god of Darkness, Dar'Karon. It is an unfathomably powerful sword that is said to be able to devour the souls of the entire universe. The only known way to destroy the Soul Cutter, as well as all the other Shaharan Artifacts, is to throw it into Mount Eruptor, the largest, hottest, and most magical volcano in the universe.
The Soul Cutter is a long black blade made of void metal that provides the wielder with the ability to absorb souls into the blade upon contact, if the wielder wishes. Upon absorbing a soul, the blade gains a charge, allowing the wielder to cast a Necromancy-based spell at will, equal to the amount of charges the blade has. Upon doing this though, the blade loses a charge for each spell cast using it. The blade, being bound to Dar'Karon, allows a mortal wielding it to command him at will, and there is a small fiery eye-like gem in the hilt of the blade that, when removed, pulls Dar'Karon back to the blade. This is the only artifact that has a clear way of summoning the god that it's bound to.
Strong All Schools; CL 50; Weight: 20 lb.