Caspian X was born in 2290 NT, and is the only child of Caspian IX and the rightful heir to the throne of Narnia. When Caspian was a small boy, his uncle Miraz secretly killed Caspianís father in order to gain the crown. As Miraz has no children of his own, he is willing that Caspian be king after him and raises his nephew as the future ruler. Although not taught about Narnia before the Telmarine reign, Caspian nevertheless learns about the Old Narnia in secret, first from his old nurse, and then from his tutor, Dr. Cornelius.
One night in 2303 NT, Caspian is awakened only to be told that his life is in danger because Miraz' wife has just given birth to a male heir. Caspian escapes before Miraz can murder him, and happens upon the Narnians of Old in the forests. The Narnians accept Caspian as King and help him plan to fight against Miraz. After blowing Queen Susan's Horn, the Pevensies arrive from the past to aid Caspian in the fight and Miraz is defeated, and Caspian is crowned King of Narnia.
Three years later Caspian sails eastward to find the seven lost Lords of Narnia. Early in the quest they happen upon Edmund, Lucy and Eustace, who joins them in their journey.
Caspian succeeds in accounting for all of the lost lords, and falls in love with Ramandu's daughter on the star's Island near the end of the world. After finishing his quest, Caspian brings his love back to Narnia, where they are wed and later have a son, Rilian.
Many years later, in 2345 NT, Caspian's beloved wife is murdered by an enchantress in the form of a serpent. Rilian, desperate to avenge his mother's death, goes searching for the serpent but is put under a spell and goes missing for more than ten years. In 2356 NT, Caspian, despairing, boards a ship to sail east again, in hopes of finding Aslan or completing the journey that he had not been able to finish, which was to sail as far east as he could and find Aslan's Country.
But before he can travel far, he is met by Aslan who tells him that Rilian has been found. He goes back to Narnia as soon as he can, but only just arrives and sees his son one last time before he dies at the age of 66.
Upon dying, Caspian arrived in Aslan's Country, in the prime of his youth. There he is surprised to see his old friend Eustace, and asks Aslan if he may just get a glimpse of Eustace's world just once. Aslan allows him to go there very briefly to aid Eustace and Jill in the punishment of some school bullies before he is summoned back to Aslan's Country, where hestays forever in the company of the Faithful of Narnia.