Batreaux

Batreaux (bat-troe) is a character in Skyward Sword. He is depicted as a demon that wishes to be human. Link can help him fulfill his wish by bringing in the Gratitude Crystals that the young hero collects throughout his adventure. Upon doing so, Batreaux will give Link various upgrades as a reward.

Trivia

 * Batreaux is similar to the Mad Batter of A Link to the Past and Link's Awakening as both are characters who take bat-like forms and upgrade certain aspects of Link.