Majora was a ancient half dragon half human princess who was sealed away by the four Light Spirits in the Temple of Time because her anger and insanity was corrupting the mask because of her evil uncle. It would later be unsealed by a unwitting Link, leading to the boy having to go on a quest to stop it and transform it back into a princess.
Majora's primary appearance is that of a purple dragon humanoid teen wearing robes laced with black and white. her arms have multiple stripes extending from them. Four multiple color spikes covered in veins extend from it's back
The dragon Majora emerged from the earth along with the rest of his race to retain balance between light and dark, fleeing when Demise fell upon him. He then associated with a dragon-human tribe, leading them to train his granddaughter to use a fraction of his power to protect their home from evil. However, she and the tribe were defeated upon their incursion into the adviser's territory at Hyrule's Castle. She was sealed away into the Temple of Time, with the Master Sword acting as the lock for her seal.
Majora slept until a squire Link discovered that he had lost his master's sword by the tricksters. Wandering into the Temple of Time, he drew the Master Sword which freed Majora's dark magic from her prison. The trickster put on the mask and using it's power, He use it teleported Link out of Hyrule Castle and lifted it into the skies. However, the young squire survived and discovered a Air Cannon. Using this, the young hero made his way to the ruins of Skyloft. Discovering a Loftwing, he then flew towards Hyrule Castle in order to slay the demon.
Upon entering Hyrule Castle, Link traversed the massive building on his way to Majora's mask thief. Defeating each of the four guardians guarding the keys to the room the mask thief was in, he finally made his way to the warlock was no match for the Blade of light and fell to Link. As he died, Hyrule Castle fell to Earth, finally landing in it's correct place.
Majora is a powerful magic user, being able to easily lift Hyrule Castle into the skies. As well, she can channel her magic into powerful elemental attacks that can do a large amount of damage to foes. Majora's tendrils are able to channel this magic and can also be used as melee weapons in battle. Majora can resist most non-magical weapons and weaker spells without much effort. Majora can also create energy wings that grant him the power of flight.