Valoo

In The Wind Waker, the Great Valoo is the almighty Sky Spirit.

Biography
Valoo resides at the top of Dragon Roost Island and is the patron deity and protector of the Rito people that dwell there. Valoo only speaks the ancient Hylian Language, so only few can understand him, and even his attendant, Medli, has trouble sometimes. Valoo grants the Rito their wings when they come of age, and always protects them from harm. When Link first visits Dragon Roost Island, he finds out that Valoo is in a bit of a predicament: he is being tortured by the tremendous monster Gohma, hidden in the mountain beneath Valoo's high peak. Due to his change of temperament, it has prevented young Rito (such as Prince Komali) from reaching him to receive the scale that allows them to grow their wings. Moreover, one of Valoo's recent rampages caused a boulder to come crashing down the mountain, breaking the bridge leading to Dragon Roost Cavern and plugging the nearby spring. Link must defeat Gohma in order to heal the Sky Spirit's pain and receive Din's Pearl from Prince Komali.

After saving the great Valoo, he recognizes Link as a true hero and also tells him to use the wind god's wind to aid the young hero on his quest. Later, after Link visits Greatfish Isle, it is Valoo who tells Quill to give word to Link about the whereabouts of the Water Spirit Jabun.

Just before Link and Tetra are about to be killed by Ganondorf when they travel to the top of Forsaken Fortress, it's Valoo, Komali, and Quill who rescue them. Valoo unleashes a blast of fire onto Ganondorf's viewing platform in an attempt to kill him. However, just before Valoo departs, the Sky Spirit warns the King of Red Lions that "such simple" fire cannot possibly destroy Ganon.

Super Smash Bros. Brawl
Valoo appears as a trophy and sticker in Super Smash Bros. Brawl.

Theory
His relationship to Volvagia (Fire Temple's boss in Ocarina of Time) is unknown, but the location of Dragon Roost Island (in relation to the rest of Hyrule) is notably similar to Death Mountain; Volvagia is the dragon from Death Mountain, so it is possible that Valoo is of a relation to Volvagia.

Trivia

 * Valoo bears similarity to Hooktail from Paper Mario: The Thousand-Year Door, being both red dragons with hook-tails.