Majora

Majora was an evil being plaguing Termina in ancient times. Majora's Mask was an accursed items used by an ancient tribe in its hexing rituals by having it bestow wicked power upon its wearer. It has recently been debated that the tribe responsible for creating Majora was in fact the Twili, as Midna and her armor both bare a small resemblance to the mask. However, it may resemble the final form of Majora's Mask or possibly the form taken by Midna when she uses the Fused Shadows to access Hyrule Castle. (The game seems to emphasize the eye on her helmet, which is similar to the eyes of Majora's Mask.)

In the manga, the Fierce Deity defeated Majora just by talking him into dancing. This dancing led to Majora to his demise and left nothing but his magic armor behind. The Fierce Deity took a feather from his head and turned it into a sword, and then took a piece of the armor and carved out the mask, sealing away the power of Majora. This is vastly different from the game's storyline.

The Skull Kid, wearing Majora's Mask, still doesn't take on Majora's mind or personality; he is simply possessed by the Mask. At the end of the game, inside the Moon, Majora manifests out of the mask into Majora's Mask, then Majora's Incarnation, an insane being that dances around the boss chamber. After the Incarnation is defeated, Majora's transformation is completed, and the Incarnation becomes Majora's Wrath. Majora is eventually defeated, and the being itself disintegrates. The mask is left behind, cleansed of the evil inhabiting it.