Long ago, the land of Equus was once perfect and good. But Abaddon, the evil Dark Horse, tricked the equines into rejecting their loyalty to their Creator, the Great Horse. As a result, a curse fell upon the equines, dooming them to eternal enslavement. But there is still hope.
Two young mustangs name Sierra and Shadow have been chosen by The Great Horse to raise His Son, the Light Horse, who is destined to break the Curse of Evil and rule as the eternal King of equines. However, Abaddon will stop at nothing to prevent the birth of his opponent. If the Prophecy of the Light Horse is ever to be fulfilled, Sierra and Shadow must chose: give in to fear, or trust in the Divine Ones and their plans.
Four years have passed since the First Stage of the Prophecy of the Light Horse was fulfilled through the miraculous birth of Soter, Son of the Great Horse. Now, Soter leaves His herd to begin His mission to break the Curse of Evil, freeing the cursed equines from enslavement to Abaddon the Dark Horse.
Soter befriends seven young stallions and appoints them as His first of followers, His apprentices. He then travels across the Great Plains, teaching the Mustang herds about the Divine Ones, and performing miracles of healing and restoration. But not everyone is convinced that Soter is the Light Horse. As conflicts of opinions rises among the herds, Soter’s friends are about to discover that there is more to the Prophecy of the Light Horse than they’ve even realized.
Soter the Light Horse has finally broken the Curse of Evil and returns to the heavenly Great Paradise as King. But the war between good and evil is far from over. Even in his weakened state, Abaddon the Dark Horse will use all of his power to seek his revenge by destroying the equines.
Meanwhile on Equus, Stone, Lightning, and the rest of Soter’s faithful band of apprentices begin their own mission to recruit equines around the world to join Soter’s Herd. But such a task is not going to be easy, for there are still enemies seeking to stomp out Soter’s memory forever. Among them is Wolf, King Wildfire's ruthless deputy, who carries out orders in hunting down Stone and his friends. But the Light Horse has different plans.
Years after the founding of the Soter Herd, a mysterious stallion steps in the scene, captivating equines around the world with his strange powers. Many are convinced that the Light Horse has finally returned, but Aurora, Soter’s half-sister, and her mate Midnight have suspicions.
Upon a shocking discovery, Aurora and her family join forces with other equines to uncover a secret plot to take control all of Equus. But they are about to be hurled into what will become the last, epic battle between the Light Horse and the Dark Horse. This time, only one will claim the title “King of Equus”.