Stone Mask

The Stone Mask is a mask in The Legend of Zelda: Majora's Mask. Though it is not needed to complete the game, wearing the mask allows Link to move about unnoticed by people and most enemies, possibly through a powerful magic. Only a select few can see through the mask's magic. Even Link himself is unable to see through the strange powers of the mask when it is worn by another character.

Originally held by Shiro, an inconspicuous soldier lying nearby Ikana Canyon, he will give the mask to Link in return for either a Red or Blue Potion to revitalize his spirits. Shiro indirectly reveals that Link is affected by the mask's power when someone wears the mask, as he can only see Shiro when looking through the Lens of Truth.

''You got the Stone Mask! Wear it with (C) to become as plain as stone.''

Tactics
The Stone Mask is used whenever Link must not been seen, but it can never be used underwater. It can be used to avoid being seen by the Deku inside the Deku Palace, should Link choose to return to retrieve either Magic Beans or a Piece of Heart.

In addition, the mask is primarily used in the Gerudo Fortress to allow Link more freedom in exploration. Curiously, the mask's effect is rendered null in the room containing the Hookshot, nor in the battle rooms with the "Super Gerudos." These Gerudo acknowledge that Link is wearing the mask though, proving that it may be due to years of training and careful concentration that they can see through the mysterious enchantments. Thankfully, only the room containing the Hookshot has other Gerudos in it, so the only way Link can be captured in the battle rooms is by losing.

Lastly, the mask is also useful for avoiding unnecessary confrontations, particularly in the Stone Tower Temple where hearts can be difficult to find.