Soul Edge (3.5e Equipment)
From D&D Wiki
Consistently referred to as the "evil sword", Soul Edge has a reputation for devouring souls. The weapon is also known to be a shape-shifter – which form it takes depends on its current owner. Only those with great mental discipline can retain their will while wielding this weapon. In the games, a common trait of selecting Soul Edge as a combative weapon is that it depletes the health of the player whilst giving increased attack power or even draining an opponent's health upon contact. Either way, it is not unusual for the player to lose the battle as a result of wielding the weapon - without the opponent actually landing the finishing blow - thereby living up to legend of "consuming" its wielder.
While Soul Edge is commonly depicted as a sword, he takes on many shapes and forms throughout the series, either through time periods or various characters wielding him. When he first gained his parasitic powers, he was a broadsword with a collection of flesh growing at the hilt and handguard area with a yellow eye. In Soul Blade, he was a normal sword with a flesh-like hilt and handguard with hooks on the latter part. When Siegfried took hold of the sword, the hooks gripped his hand tight to keep him from discarding him. By the time Nightmare arose, the weapon transformed into a giant sword with flesh filling the blunt side of the blade and the eye at the base of his hilt. One side of the sword featured an enlarged blade to greater fit Nightmare's fighting style.
damage: 6d8 plus 5d6 unholy damage. when character is attacking, she can offer up hit points for added damage, and drains HP from opponent equal to half the damage inflicted, however, character is constantly at risk of being corrupted by the sword. If corrupted, the sword takes over their soul, and character must now constantly feed the sword with souls of warriors and innocent alike.