Wart

Wart (ワート, Waato) is a Mini-Boss in Majora's Mask. It is a huge eye that rolls around trying to hit its enemies. At the start of the battle, Wart is hovering slightly above the ground, completely surrounded by a mass of bubbles, rendering it immune to any damage. In order to defeat Wart, Link was forced to use his range of weapons to knock the bubbles off of Wart, then eliminate them before they could reattach themselves. If a bubble managed to reattach itself, Link would have to forcibly remove it again. When Wart opened its eye, unobscured by its bubbles, Link could attack it, preferably with his bow, until it fell to the ground, dropping any bubbles still clinging to it. Wart would then begin rampaging through the room, charging from wall to wall in an attempt to kill Link, but its weakness hadn't changed. After a few more arrows, Wart was defeated, leaving no corpse as it exploded, revealing the treasure it had protected.

Strategy
Wart is a time-consuming enemy. The sheer amount of bubbles on it make it a long struggle to pierce its shield, as it is constantly moving, along with Wart, which will differentiate from retreating to trying to press itself against Link in an attempt to cause damage. The bow is not a good idea at this point, as there are simply too many bubbles. Any offensive weapon is capable of removing the bubbles, although the best is the bomb, which knocks many bubbles off at once. Using the Hookshot is another way of removing the bubbles, although it is a time-consuming way. The bubbles are incapable of being destroyed while on Wart, only knocked off, which makes them even more of a pain. When an opening is finally made, and Wart's eye is no longer blocked by bubbles, the bow is the way to go. After enough shots, Wart will enter stage two, forcing its surviving bubbles off its body and begin rolling around wildly. First finishing off any bubbles, then attack Wart with the bow. After a few more shots, Wart will be finished.

Trivia

 * Wart also has a resemblance to Arrghus, and Vitreous, who you kill in the same manner — Arrghus also shares Wart's name in the Japanese version of A Link to the Past.
 * Wart also appeared in the Secret Shrine, defeated in exactly the same way.
 * A frog-like character named Wart also appeared in Doki Doki Panic (or, Super Mario Bros. 2). This character differed drastically from the Wart of Majora's Mask. Interestingly, this Wart made a cameo appearance in Link's Awakening, with his Japanese name, Mamu Mamu.