Revali is a character in The Legend of Zelda: Breath of the Wild. He is also the Rito Champion and one of Link's allies, even though he considers himself his rival. He wears the same blue clothes as Daruk, Urbosa, Mipha, Link, and Princess Zelda. He was gifted with the power to create updrafts, helping him fly with ease. Revali is also a formidable archer, wielding the Great Eagle Bow, a bow that is normally to heavy for a Rito, implying that Revali has great strength.
For the moment Revali's role in the Zelda series is only composed of informations with an unconfirmed timeline placement and should stay this way until we have a definitive answer, so please don't add any information regarding the timeline placement without OFFICIAL confirmation, thanks.
100 years before The Legend of Zelda: Breath of the Wild
Revali lived in Rito Village with the other members of his race before he was chosen by King Rhoam Bosphoramus Hyrule and Princess Zelda to become the Rito Champion and the pilot of the Divine Beast Vah Medoh, thus becoming a protector of Hyrule and one of the most valuable asset of the Hyrulean army for their goal, defeating Ganon.He helped Zelda's group to improve their efficiency for this task and was caught off guard by Ganon emerging from Hyrule Castle, was sent by the Princess to his divine beast to start the counter attack only to be killed by Windblight Ganon who was waiting for him.His Spirit was then trapped inside the Divine Beast by Ganon's creation.
The Legend of Zelda: Breath of the Wild
During Breath of the Wild, Revali's spirit was freed by Link a century after his death at the hands of Windblight Ganon, he blessed Link with the use of Revali's Gale to thanks him.He then conduct Vah Medoh to its firing position and waited for the battle between Link and Ganon admiting that Link is beter than him.When Link finally faced the monster, he along with the other Champions fired a large laser beam in order to weaken Ganon allowing Link to destroy the physical form of the beast.