Fierce Deity (Deity)

The Fierce Deity is Hylia's Knight, and God of the Sheikah. He first appears in Majora's Mask and is last mentioned in Skyward Sword. Like other Sheikah, he bears white hair, a dark blue bodysuit, and armored plating over his tunic. However, his eyes are white rather than blood red or amber gold. in addition, he towers over every any other incarnation of Link. The metal plating on his tunic bears a Triforce piece, and a Crescent Moon symbol on the left and right breasts respectively.

First Appearance Symbolism
Termina's Kaepora Gaebora's mentions him, adding that though "this guardian has lost its guard deity, it was doomed to fade anyway." At the Ending of Majora's Mask, Link earns the Fierce Deity Mask. As is keeping with the game's theme of sealed souls within masks, and a precedent in Majora's extricating the Butler's Son's soul, it is very plausible that Fierce Deity was sealed by it sometime before the events of the game.

The reason for Majora's giving you the mask is nebulous. One likelihood is that Link's action in helping Termina and the four Mask Tribe, revived the role of the land's guardian, by inadvertantly becoming it in all but name. Therefore, Majora recognized Link as an adversary worthy of donning the power which defeated it once; for a vengeance match. Another is that since Link is interacting with the past, he is only reliving events predetermined to happen and Majora has little influence over the dimension, and by extension his host's actions. It could be the mask's own power that sought Link out, to the end of defending Termina from the demon.

Furthermore, it's a matter of question where the final battle even occurs, but there are some notions. Given the astrological arrays that ornament it and Fierce Deity's armor, the dark blue color not correlative to Majora's erratic rainbow theme but kilter to the Sheikah shrines in Breath of the Wild, and the fact that all the Boss Masks are found hanging there; it stands to reason that this is a holy place for the Mask Tribe, and as such likely their god, Fierce Deity's, throne room hijacked by Majora. There, the true mask sleeps, absorbing the power of the other Boss Masks, until Link awakes it.

Relevance in Hyrule
In Skyward Sword, he is only ever mentioned by Fi and indirectly by Demise, in admiration of Link's humanity. The game is very careful not to confirm whether Denise or Impa have ever seen him, which suggests, that either he sacrificed his divinity like Hylia and died, or was otherwise sealed in an event before Demise's defeat. The extrapolation of his divinity, is roundabout, but has to be true, else he would have been trusted to make the wish on the Triforce for Hylia, and Skyloft would not have been needed.

Meaning of Name
Fierce Deity's name is an object of some contention among the English fanbase, because of the insinuation that it carries evil by the description text and by the Majora Child's dialogue. However, in the native version, the mask carries no such ill connotations, as the Majora Child is referring to Oni-gokko, the Japanese game of tag. In it, the "Oni" is 'It,' hence Majora's second form which evades Link. Since America has no English equivalence, the idea of the demon, Oni, came to be incorporated in flavor text.

The actual Japanese name is "Kishin" (鬼神). 鬼 by itself does mean oni, but when you put two kanji together it creates a different meaning, and the 鬼 part becomes more akin to "fierce" or "relentless." Together the meaning is "fierce like an oni." 鬼神 is a real term in Shingon Buddhism but for an audience that will probably not be familiar with that, Fierce Diety is as close a translation as any.

Controversy
In a Game Informer interview from March 2015, Eiji Aonuma revealed his thoughts on the identity of the Fierce Deity soul, stating: "The best I can give you is just a suggestion. The best way to think about it is that the memories of all the people of Termina are inside of the Fierce Deity Mask." This supposition of a mask made of "memories" is unfounded, and results from his not being the script-writer. Nevertheless, it is deducible his take on the matter came from working on the text for Majora's Mask 3D. The only direct reference to the Fierce Deity Mask in the game, states: The Fierce Deity Mask, a mask that contains the merits of all masks, seems to be... somewhere in this world... Aonuma no doubt understood this to be a sort of Easter Egg, but it's actually describing why only with the Fierce Deity Mask can you observe the full ending of Majora's Mask, because despite Link having no other masks after obtaining it (aside from the three transformation masks), the good ending of every sidequest in the game still occurs. This is because masks are retainers of people's feelings. If Link doesn't have a particular mask, the ending scene for that mask will be blacked out accordingly for the same reason. The Fierce Deity Mask is a retainer for the merit of resolving the feelings of all the people of Termina. However, it's a misdirecting to say this is the soul of the mask. Then again, this could be what Aonuma intended to say, and his evasive answer was deliberate to avoid giving away too much of Zelda's story.

Trivia
1. Skyward Sword Link can fire Skyward Strikes like Fierce Deity Link's light beams.

2. Lizalfos is the only non-boss enemy that can be damaged by Fierce Deity's light beams.

3. When the Light Spirits retaliate against the Dark Links in the Lanayru flashback cutscene from Twilight Princess, the leader who has possessed Link, has his eyes turn to white beads, reminiscent of Fierce Deity Link's white eyes.

4. It's interesting that Grog also has white eyes and sits under a tree stump like the Majora Child, above which a Skull Kid plays.