Moon

The moon was a puppet of Majora's Mask during Link's adventure in Termina, it's menacing visage demonstrating it's malevolent nature. By the power of Majora's Mask, it had been pulled from its orbit, threatening to crash into Clock Town, which would obliterate the town, along with most of Termina.

One of the interesting points of the moon is that it always faced south. Another thing is, is that inside of it was a beatiful meadow, hazy like a dream; the only thing to break the scene was a single tree. The moon was stopped from its path by the Four Giants, after Link freed all the giants he played Oath to Order beseeching the Four Giants to come to the aid of the people of Termina. The moon then became possessed by Majora's Mask, which manipulated it into opening its mouth, its eyes started to glow, and it said:

"I- I shall consume- consume- consume everything."

The moon was the scene of the final battle in the game, and it seems that it was destroyed afterwards. The moon was one of the many mysteries of Termina that will probably never be solved.

Other games
In the Wind Waker, in the Nintendo Gallery, there was a sculpture of the moon in the background behind the counter.

In Super Smash Bros. Melee, the stage "Termina: Great Bay" had the Moon from Majora's Mask in the background. As the match continued, it would slowly descend (not affecting the match in any way). The Four Giants would also come and push the Moon back up. There was also a trophy of the Moon that could be collected in the game.