Fierce Deity Link also known in japanese as Fierce God Link and Ogre Deity Link in manga and the video game is the spirit that inhabits in Fierce Deity mask and the true main protagonist in The Legend of Zelda: Majora's Mask. He is known to be the Termina alter-ego of Link and has the voice of the adult Link from Ocarina of Time. He has the size of Adult Link from Ocarina of Time and has the double helix sword to defeat 4 bosses and Majora, he is voiced by Nobuyuki Hiyama who has voiced the adult Link from The Legend of Zelda: Ocarina of Time as well in Soul Calibur 2 in Gamecube version and also voiced the anti-hero BlackWarGreymon in the Japanese dub version of Digimon Adventure 02. Fierce Deity Link is not an villain in the game, despite his brutal appearence, Fierce Deity Link has no pupils on his eyes, he has his armor, he has the tattoos on his face with blue and red and he has white hair. His appearence is an Adult-like form with the Fierce Deity Sword called Double Helix Sword when Link becomes his famous alter-ego.
In the manga, he speaks, but in the video games, he does not. But he uses his frequent cry and shout to target the monsters just like Adult Link before him.
Fierce Deity's Mask first appears in Majora Boss Battle when Link dons all non-transformation masks to Lunar Children, the five child with Majora's Mask gives Link an Fierce Deity's mask and challenges him in a boss battle for the fate of the Termina. Link releases the Bosses Remains in each side, awakening Majora who tries to attack Link. But Link uses the Fierce Deity's mask and transforms into his alter-ego named Fierce Deity Link who ressembles Adult Link from Ocarina of Time except with an Fierce Deity armor, tattoos on his face, white hair and white eyes with no pupils.
As Fierce Deity Link, Link manages to kill the Bosses Remains before going to attack Majora, Majora then changes into Majora's Incarnation to continue his fight with Link. But Link attacks him again with his Fierce Deity Sword, hitting him before turning into Majora's Wrath. Angry, Majora tries to attack Link, but Link uses the powers of the Fierce Deity with Sword beams multiple times on Majora, causing Majora to disintegrate into dust before reverting back into a lifeless mask form, this time for good. The Moon disintegrates into rainbow of light, saving Termina in the process.
Link then reverts back to normal and tells the Happy Mask Salesman to guard the now-lifeless Majora's Mask for good in which this latter agrees. As Skull Kid, The Happy Mask Salesman and Link part ways. Skull Kid draws Link and him to be friends with him.
Fierce Deity Link appears in Hyrule Warriors and Hyrule Warriors Legends in the Majora's Mask DLC when Young Link transforms into Fierce Deity Link, he is also an ally to Link. However he appeared in The Legend of Zelda: Past and Present when Link finds the Fierce Deity mask to transform itself into this one to fight Dark Link.
Fierce Deity Link is voiced by Nobuyuki Hiyama, who is better known for the voice of Adult Link from Ocarina of Time, Soul Calibur 2 GameCube Version, in two games of Super Smash Bros. series, he is better known for voicing the anti-hero BlackWarGreymon from the Japanese dub version of Digimon Adventure 02.
Nobuyuki Hiyama is the one who reprised the Fierce Deity Link's voice in Majora's Mask 3D and in Hyrule Warriors via Majora's Mask DLC as a transformation of Young Link who is also called Link.