The Fierce Deity set in “The Legend of Zelda: Breath of the Wild” is a costume for Link that is based on the Fierce Deity character from “The Legend of Zelda: Majora’s Mask.”
The armor set is composed of the Fierce Deity Mask, Fierce Deity Armor, and Fierce Deity Boots. Each piece of the set provides 3 defence points, and the set provides an attack up bonus in Tears of the Kingdom. The Fierce Deity Armor set also increases Link’s attack power.
This set can be obtained through the use of a specific amiibo with the game’s amiibo Rune feature. The amiibo needed is the Link (Majora’s Mask) amiibo, which was part of the Super Smash Bros. series of amiibo figures. The items are not guaranteed to drop and may require multiple attempts.