Gibdo Mask

The Gibdo Mask is given to Link by Pamela's Father in Majora's Mask.

Location
The mask is obtainable after Link lifts the curse cast upon Ikana River in Ikana Canyon. Then, upon entering the Music Box House, the young hero finds Pamela's father in a state of half-mummification. By playing the Song of Healing, her father will be healed, and the mummified portion of him encased in a mask. Despite its ghoulish appearance, the Happy Mask Salesman will still recognize that it is "filled with the love of a father and child".

Uses
The mask causes Gibdos and ReDeads to recognize Link as one of their own, and so they will not attack him. While wearing the mask, Link can in fact talk to Gibdos, which is necessary to explore the Gibdo Well, which is, at first, the only way to enter the Ancient Castle of Ikana (and thus proceed in the game). ReDeads cannot be talked to, but the mask will cause them to dance, rendering them inoffensive.

Trivia
The Gibdo Mask is one of six masks that are necessary to complete the game, the others being the three transformation masks, the Garo's Mask, and the Captain's Hat.