Batreaux

Batreaux is a character from The Legend of Zelda: Skyward Sword. He is a friendly, bat-like demon residing in a shack below Skyloft, with a fondness for humans.

Biography
At one point in the game, the child Kukiel is reported missing by her parents, Jakamar and Wryna. Link asks around Skyloft for clues, and eventually hears tales of the demon from Rusta at the Lumpy Pumpkin. Following the old man's advice, Link strikes one of the gravestones in Skyloft's graveyard at night, granting him access to Batreaux's House, from which Link hears a terrible scream emanate. Once inside, Batreaux is seemingly poised to strike Link, but once Link attempts to swing his sword at him, Batreaux begs him to stop and not harm him. Batreaux (Human)

Batreaux explains that he and Kukiel were merely playing a "scream-as-loud-as-you-can-game"; Kukiel is, in fact, the first human not to scream at the sight of him. He tells Link of his utmost desire, which is to become a human; to achieve this, he asks for Link to retrieve Gratitude Crystals, physical manifestations of people's happiness found throughout areas of The Sky populated by humans. In return, he gives Link several useful items such as wallets, Rupees, a Piece of Heart, and a Cursed Medal, though he warns Link not to open the chest containing the latter.

When Link has gathered 80 Gratitude Crystals, Batreaux is transformed into a human, though his human form turns out to be almost identical to how he looked as a demon. As a result of his transformation, the evil aura he used to emanate, which caused copious monsters to swarm the island at night, and Remlits to transform into vicious monsters, also disappears, making Skyloft safe at night again.