Hero Wielding the Sword that Seals the Darkness

The Hero Wielding the Sword that Seals the Darkness is a character mentioned in the The Legend of Zelda: Breath of the Wild. This hero fought Calamity Ganon alongside the four Divine Beasts and a Princess With A Sacred Power 10,000 years before the events of the game. Using the Master Sword, he was the one who delivered the final blow to Calamity Ganon. During the course of the game, the story of the hero is related to Link by both the King of Hyrule and Impa.

Theory
It seems likely that the Hero Wielding the Sword that Seals the Darkness is an incarnation of Link. He is depicted wearing the same outfit as Link from Breath of the Wild. Although he seems to have long red hair, which no other known incarnation of Link is seen to possess.