Originally known as Nanaki, Red XIII was the last of his species, a wolf/dog hybrid capable of human speech. He was imprisoned as an experimental subject by Hojo of ShinRa Inc., who attempted to cross-breed him with Aerith in an attempt to create a Cetra with a longer lifespan. He escaped when Cloud, Tifa and Barret broke into ShinRa Headquarters to rescue Aerith.
Red XIII had always lived believing his father was a coward, but a trip to Cosmo Canyon proved that his father had been protecting their homeland all along. He continued to accompany Cloud in pursuit of Sephiroth, and returned two years later to assist AVALANCHE in battling Bahamut Sin in Edge.