This two-handed longsword is used when Link uses the Fierce Deity's Mask to transform into the Fierce Deity. Aside from its long range, the Fierce Deity Sword is able to fire magical light blue-colored blasts shaped like buzzsaws, similar to Sword Beams, when used while Z-targeting is in effect; however, each such attack drains one point of magic from the Magic Meter. The sword cannot be unequipped until Link removes the Fierce Deity's Mask.
The Fierce Deity Sword deals the same amount of damage as the Great Fairy's Sword. The sword cannot be sheathed, unlike other swords that Link can use, but will be put away for the portion of time Link attempts to use a bottle. Link can use the Fierce Deity Sword to parry a small range of attacks, such as basic whip slashes from Majora's Wrath.
- "A peculiar greatsword allegedly used by a hero from a world in which the moon threatened to fall. It slashes wildly in battle as if possessed by a fierce deity."
- — In-game description
The Fierce Deity Sword is a two-handed sword which Link can obtain by using the amiibo Rune with the Majora's Mask Link amiibo of The Legend of Zelda: 30th Anniversary series. This marks the first time where the sword appears as an item in of itself.
The Fierce Deity Sword appears as part of Young Link's moveset.
While Young Link wields the Kokiri Sword, when using certain attacks (such as his Weak Point Smashs and Special Attacks) he transforms into the Fierce Deity and uses the Fierce Deity Sword. Young Link can also transform into the Fierce Deity and wields the Fierce Deity Sword while in Focus Spirit, which adds a Sword Beam effect to his combos and increasing the range of his combo attacks.
Additionally, Young Link wields his Kokiri Sword (which has a slightly longer blade) as a two-handed sword which makes the transition between the two forms more seamless. As a result, there is little overall difference between the two forms in terms of fighting style, saved for the aforementioned Sword Beams the Fierce Deity uses during Focus Spirit.
During Fierce Deity's Focus Spirit Attack, the Skull Kid wearing Majora's Mask appears (along with Tatl and Tael), summons the Moon which the Fierce Deity easily slices in two with his Fierce Deity Sword, demonstrating that the sword is incredibly powerful weapon in Hyrule Warriors. During Young Link's Victory Cutscene, the Fierce Deity will perform a few slashes with his sword before using it to attack the screen with a jumping slash causing the screen to turn white. It then shows Young Link as he is removing the Fierce Deity's Mask.
Two more unnamed variations appear corresponding with the Furious Deity and Vengeful Deity weapons, though they share the weapon's double helix blade design.
| Link · Princess Styla · King Tuft · Madam Couture|
—Full list of characters
|Arrghus · Blizzagia · Margoma · Moldorm|
| Hytopia · Woodlands · Riverside · Volcano · Ice Cavern · Fortress|
—Full list of locations
|Gripshot · Bomb · Boomerang · Bow · Fire Glove · Gust Jar · Hammer · Water Rod|