Pegasus in Fate/stay night is not a standalone character but rather the noble phantasm and familiar of the Rider-class servant, Medusa. Summoned during battles, Pegasus is a divine, winged horse from Greek mythology that Medusa rides into combat. With tremendous speed and magical power, Pegasus enables Medusa to unleash devastating attacks, especially her Noble Phantasm 'Bellerophon.' Pegasus symbolizes Medusa's mythological origins and adds a significant edge to her abilities during the Holy Grail War.