"The Ebony Blade, sometimes called the Vampire or the Leech, resembles an ebony katana, and its power is very dark indeed. Every time the Ebony Blade strikes an opponent, part of the damage inflicted flows into the wielder as raw power. The Blade itself may not be any more evil than those who have used it, but at some point in its history, a charm was cast on it so it would not remain with any one bladesman for long. The wizard who cast this charm sought to save the souls of any too infatuated by the Blade, and perhaps he was right to do so."
The Ebony Blade is a powerful Daedric artifact connected to the Daedric Prince of Murder, Mephala. In order to gain the weapon, Mephala must be summoned on the 13th of Frostfall (Witches Festival) and take her quest to prove their worth.