The Demon Lord's Right Hand (3.5e Equipment)
From D&D Wiki
This +2 Keen Demonic Mercurial Longsword was forged in the depths of the Nine Hells by a Fallen Sword Archon, whose true name is long forgotten. Alone it is a powerful weapon, especially fatal to Good Outsiders, but when the rest of the Demon Lord's Raiment is brought with it, the wielder becomes a truly formidable foe. The Demon Lord's Right Hand is long, with wicked recurved barbs along its blade, and veins of dark red laced throughout. The crossguard and pommel appear to be in the rough as they are jagged and sharp, though the hilt itself appears smooth. When the sword is wielded, the crossguard immediately grows and completely encloses the wielder's hand and wrist. No piece of this set has been seen on the Material Plane as of yet.
Aggregate Extra Stats: - Adds 1d6 Evil damage which is immediately absorbed as Hit Points. - Deals double damage to Good Outsiders - Can only be wielded by especially chaotic and evil characters, any Evil outsider or a character with a Demonic Graft.