Description
Carnwennan, or Carnwenhau, meaning "white hilt" was the dagger belonging to the great King Arthur. It is attributed with the magical power to shroud its user in shadow. This dagger, it is said, was one of three sacred weapons given to King Arthur by God.
Arthur names it as one of the few things in the world which he would not give to his cousin Culhwch.
King Arthur used this very dagger it to slay the witch Orddu ,daughter of Orwen. by slicing her in half. It is also possible that this is the dagger he once used to kill a giant.