The Oathkeeper

Source
This item is a world drop.

Trivia

 * The Oathkeeper is an Epic Weapon card in the World of Warcraft: Trading Card Game's Drums of War set.
 * This item could be a reference to The Oathkeeper keyblade from the game Kingdom Hearts.
 * This item may also be a reference to the Valyrian steel blade Oathkeeper in George R.R. Martin's Song of Ice and Fire series of books.