Fierce Deity

Fierce Deity is a character from The Legend of Zelda: Majora's Mask. The assumed name of the spirit that inhabits the Fierce Deity's Mask, there are very few facts truly known about Fierce Deity, and his background is one of the many ambiguous plot holes that tie together the overall story of Majora’s Mask.

When Link dons the Deku Mask, Goron Mask and Zora Mask he transforms into the spirit of what is presumably the Deku Butler's Son, Darmani and Mikau, respectively. Due to this, it has come to be presumed that the spirit inhabiting the Fierce Deity’s Mask is that of a great god, possibly even a devil due to Fierce Deity's name translating from Japanese to the “Devil God”. When Link uses any particular transformation mask, he takes the shape of what the spirit inhabiting the mask looked like during its lifetime. Using this knowledge, it can be surmised that Fierce Deity was a tall warrior god, who wielded the Double Helix Sword that was capable of shooting Sword Beams. Also, it is possible that Fierce Deity somehow met his demise, and his spirit is all that remains.

History
Though the history of Fierce Deity is never elaborated upon in the game, it is implied, through what is said by the likes of Tatl, and the fact that Majora himself gives Link the god's mask, that the Fierce Deity's Mask was created by a Deity far stronger than Majora, and that Majora could possibly have given the mask to Link in an effort to destroy them both. Fierce Deity's evil may be even darker than that which resides in Majora's Mask, as Majora calls him "the true bad guy", though this may just be a lie or exaggeration on the part of the insane Majora, and that Majora considers itself a hero.

Other theories suggest that Majora is simply insane. It is possible that Majora gives Link the mask because, as it suggested, it simply wanted to play. This is a recurring theme in the game. Examples include: Majora transforming Link into a Deku instead of killing him, the way that Majora chooses to raze Termina by crushing it with its Moon, Majora transforming Kafei into a child three days before he was supposed to be married, and that it gives Link the Fierce Deity's Mask before their final battle. The Fierce Deity's Mask could be a way of evening the odds; a sense of fair play, in that Majora and Link would be equal in terms of power.

Another possible theory is that Fierce Deity is the masked incarnation of Link's Terminan counterpart, due to the resemblance between him and Link. This is supported by the fact that almost every inhabitant of Hyrule is believed to have a counterpart in Termina, except Link. If Fierce Deity is Link's counterpart, it would explain Link's apparent lack of a counterpart. This could be considered to either be supported or debunked by the info of the mask saying that it is filled with dark power. If Fierce Deity is Link's counterpart, it may in fact be his dark or even evil opposite. Another possibility is that the Ancient Ones who sealed away Majora's Mask worshipped Fierce Deity and that the deity's spirit is trapped inside the mask.

The Fierce Deity may also be the very first incarnation of Link from The Legend of Zelda. Although Link never reached adulthood in the original game, he does wear a blue tunic after buying the Blue Ring. The tunic looks exactly like the Fierce Deity's tunic, but has no decoration. After defeating Ganon, he may have reached adulthood, died, and then been ordained as the Fierce Deity to watch over the Earth. Like the other deities, such as Din, Nayru, and Farore, he may have sealed his spirit into a powerful object such as the Triforce.

In the manga
It is explained that Majora's Mask is carved from the hide of a powerful dragon, Majora. Majora guarded an empty land that was neither moving nor dead. This dragon's armor was sought after, as it was believed that the armor could grant wishes and give power. Many came hoping to claim the armor for their own reason, be them good or evil, but Majora killed them all. One day, a mysterious man visited Majora. This man played music for the dragon, who danced for three days and three nights before dying, supposedly allowing time to move forward. The man then carved a mask from the creature's hide, hoping to seal its power.

Interestingly, the traveler bears a strong resemblance to Fierce Deity, who has darker-than-average skin, and silver hair, and it is hinted in the story that the stranger is in fact a god, although why this being chose to approach and ultimately slay the beast is never explained, other than when he says, "I was drawn to this land by a strange force". Some further evidence pointing to this being the true identity of Fierce Deity, a point is made that the stranger is the first being that is able to overcome the beast of Majora, and that it does so with music that controls the flow of time.