The Moon (月, Moon) is the main threat of The Legend of Zelda: Majora's Mask. By the power of Majora's Mask, it is destined to crash into Clock Town, which will obliterate the town along with the rest of Termina.
The Moon, controlled by Skull Kid under the effects of the titular mask, is the constant threat of The Legend of Zelda: Majora's Mask. Link is given three in-game days to save the land of Termina from the Moon's destruction (however, he can turn back time with the Ocarina of Time). Along with his Fairy companion Tatl, Link sets out to find the Four Giants in each of the temples found throughout Termina.
After they free the Giants from the Skull Kid's curse, the young hero and his Fairy climb atop the Clock Tower on the Final Day to call upon the Giants using the "Oath to Order." One by one, the Four Giants appear and stop the Moon's descent, knocking the Skull Kid unconscious in the process.
At this point, Majora's Mask realizes that the Skull Kid has become useless, so it abandons the imp's body and transports itself inside the Moon. With the Moon now being possessed by Majora's Mask, it becomes too strong for the Giants to hold back and it threatens to continue with its plan of obliterating Termina. While the Four Giants use all of their might to restrain the evil menace, Link and Tatl follow Majora's Mask into the Moon. Inside, Link defeats Majora's Mask and the Moon disintegrates, returning peace to Termina.
If he fails to do so, the Moon crashes into Termina and destroys the world in the "game over" sequence, which serves as the inspiration for the Moon's role as an Assist Trophy in Ultimate.
As a background character
The Moon also appears as a trophy in Melee.
As a background character
The Moon reprises its role as a background character in Great Bay, which returns from Melee. Its appearance has been updated to match its style in The Legend of Zelda: Majora's Mask 3D.
As an Assist Trophy
The Moon also appears as an Assist Trophy. When summoned, it appears as a miniaturized version of itself before respawning in the background and making a collision course towards the area of the stage where the opponent was when it was summoned, becoming more fiery as it gets closer. Once it hits the stage, it deals multiple hits before disappearing, doing 60% damage on a target if all hits connect. Training Mode describes the Assist Trophy: Falls from the sky and causes a massive explosion when it hits the stage. Can't be KO'd.
The Assist Trophy cannot be summoned on the Luigi's Mansion, Great Bay, New Donk City Hall, Midgar, Pac-Land, Duck Hunt, Gaur Plain, Boxing Ring, Wii Fit Studio, Gamer, Palutena's Temple, Flat Zone X, The Great Cave Offensive, PictoChat 2, Living Room, Balloon Fight, Reset Bomb Forest, Arena Ferox, Prism Tower, Unova Pokémon League, Dream Land GB, Spirit Train, Paper Mario, Golden Plains, Hanenbow, Mario Bros., and the 75m stages.