Ruby Demon Killing Knives, Supernatural

Knives to kill Ruby Demons from Supernatural. The Demon-Killing Knife, or Ruby's Knife, is an ancient knife created by the Kurds that possesses the power to permanently kill demons, hellhounds, and other demonic entities, but not the Whore of Babylon, as Castiel said only the cypress wood can. kill her. Although it somehow came into Ruby's hands, it eventually passes to Sam and Dean Winchester, who use it as their most common means of killing demons.