Hero's Spirit

In Twilight Princess, the Hero's Spirit is a skeleton-like figurehead that teaches Link each of the seven hidden skills throughout the game.

The Golden Wolf
The golden wolf is the animal incarnation of the Hero's Spirit. The wolf is summoned by a howling stone, with the exception of the first time, in which he confronts Link directly. Once a howling stone is found, the tune must then be sung in tune with the Spirit. He will then tell you to "take sword in hand, then find [him]," implying to return to human form before searching for it. The Golden Wolf is also a symbol on Link's map, which is useful in case the player forgets where the location of the Hero's Spirit is. When confronted, Link will be transported into an ancient arena, and the wolf will finally transform into his true form, the Hero's Spirit, who will then teach you one of the seven hidden skills.