The Guardians seek a hidden relic inside the Fire Realm and soon learn of the Fire Oath, a promise Gamma Ray made as prince of the Solar Herd to protect his realm at all costs.
"The herds of magical horses in Horsa have a fragile alliance, but when a prophecy stating that a yearling with a new kind of magic has been born, the four herds each elect a group of horses to find the yearling and bring balance to Horsa"--OCLC.
