Mordenkainen's Sword is a floating sword that can take instructions and fight on the side of its owner. It is summoned by the level 7 Wizard spell Mordenkainen's Sword.
Once summoned, its in-game creature name is Magical Sword.
This belongs in the comments, but, I can't seem to leave a comment. This spell doesn't have a long duration, but, it makes an incredible tank. It also does decent damage to boot.