A Gravity Child that first appear at Trick 227. He repeatedly makes manga quotes and references when talking. He is a mecha-user, and seems very smug and confident.
Percival first made his appearance after Kogarasumaru's battle with the original Sleeping Forest in the Inorganic Net, along with Gawain, Merlin, Nike and Morrigan. He later attempts to help Gawain beat Trident; he captures Benkei and holds Osaka hostage, threatening to destroy the city with his A.T. Railgun if Yoshitsune resists. Benkei frees herself, cutting off her own leg in the process, and when Gawain gives the order, Percival attempts to raze the city. Yoshitsune activates his regalia and counterattacks, creating a large pressurized defensive wall and rebounding Percival's attack, the impacting explosion of which destroys the railgun and kills Percival.
Percival's road is never explicitly stated. He seems to favor using AT-powered technology rather than his own tricks in battle.