Navi is a fairy who's instructed by the Great Deku Tree in Kokiri Forest to assist Link in his quest to stop Ganondorf. She only appears in "Ocarina Of Time".
Navi aids the player by providing an analysis on nearby items and enemies, throughout the game. When fighting Ganondorf, Navi is driven back by his dark powers and is unable to help, but after Link and Zelda escape Ganondorf's collapsing castle after defeating him, she courageously joins the fight against the monstrous Ganon. Navi and Link part ways at the end of the game, possibly paving the way for the story in "The Legend of Zelda: Majora's Mask".