Throughout the duration of the Zelda timeline, there have been a lot of mysteries that fans have been attempting to unravel for years now. From Breath of the Wild's timeline placement to the details of the Hero of Time's death, players can spend countless hours putting the pieces of these puzzles together. One of the strangest games in the series, The Legend of Zelda: Majora's Mask, has little to do with the overall timeline, yet it's overflowing with secrets and strange unanswered plot elements. Among them is the origin of the Fierce Deity, since very little is actually said about them in the game.
Unsurprisingly, Majora's Mask involves collecting various masks. Link can find them by assisting the people of Termina with their problems and each one will grant him unique abilities. Most of them offer simple powers like increased speed or invisibility, but there are a few capable of transforming Link entirely. These masks are integral to the story and offer Link some of his most substantial tools in the game.
Out of all four of the transformation masks, only the Deku, Goron, and Zora masks are necessary to complete the game, but the Fierce Deity Mask is one of the most powerful items Link can acquire in any Zelda title. It transforms Link into a towering figure clad in armor and facepaint, wielding a massive double helix blade capable of shooting beams of energy. Players have found it strange that the final boss himself will gift the mask to the player if they've collected every other mask and given them away to the children on the moon, especially since its power turns the final Majora's Mask fight into one of the easiest bosses in the entire franchise.
Zelda's Fierce Deity Mask Origin Theories Explained
While the Fierce Deity's origins aren't explicitly explained in the game, the developers of Majora's Mask seem to want to keep it a mystery. In an interview with Eji Aonuma conducted by Game Informer and reposted on Zelda Dungeon, Aonuma said, “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 could be taken in many ways, but perhaps this is in reference to all the people that Link assisted throughout his adventure. The problems he fixed were created by Majora, and the masks he received were given in gratitude for Link's good deeds. Majora says that Link is a "bad guy," so perhaps he's saying that because of how Link fixed all the issues he created and the Fierce Deity Mask literally embodies the memories of all of Termina, which is why it gives Link so much power.
Another obvious theory is that the Mask holds the spirit of Link's Termina counterpart. Termina is filled with characters who have an identical counterpart in Hyrule with varying personalities and histories. Link's counterpart is never seen, and the mask itself bears quite a strong resemblance to the hero. The other transformation masks hold the spirits of individuals who have died, so perhaps the mask holds the spirit of Termina's dead Link. Either way, the Fierce Deity Mask is one of the strangest occurrences in The Legend of Zelda: Majora's Mask, and it is unlikely fans will get a definitive answer soon.
Source: Zelda Dungeon