The First Blade is a weapon made from the jawbone of a donkey that was once connected to the Mark of Cain. The blade somehow strengthens the Mark, and when held by the bearer of the Mark, is able to kill any known being. It is also the only one of few things that could kill Knights of Hell. It is so powerful that Crowley once called it, "the most dangerous weapon on the planet." It is dangerous enough to cause fear in even angels, which the blade can also kill. However, since the Mark of Cain has been destroyed, the blade is now rendered useless and powerless.