Sfeiz is one of the Black Knight's four Swords of Darkness. While this sword is originally from YGGDRASIL, it was once in the possession of a Cursed Knight. After its owner passed away, this blade enter into circulation for at least two hundred years.
Stated by the Swords of Darkness, Sfeiz was some sort of blade that could kill a target with just the merest scratch from it. In other words, if the target did catch such a wound by this weapon, it could prove fatal for one's life. Ainz believed that one wound alone caused through the blade might be the work of an instant death effect something which a Cursed Knight possesses among its various special abilities.
- It was said that Sfeiz is classified as a death type of weapon.