The Cloak of Force is an item unlocked by defeating four colossi in Time Attack on Normal difficulty in Shadow of the Colossus. If worn by Wander, it increases the amount of damage he deals with the Ancient Sword. The effect stacks with both the Mask of Power and the Mask of Strength.
Dormin says the following upon retrieving the item:
|“||That is the 'Cloak of Force'... By wearing it, thou shalt be able to inflict more grievous injuries upon a colossus...||”|