Which magical horn summons the Pevensies back to Narnia in Prince Caspian?

Susan’s horn is the magical horn that summons the Pevensies back to Narnia in Prince Caspian.

Susan left the horn behind in Narnia after the siblings’ first adventure. Centuries later in Narnian time, Prince Caspian receives it from his tutor, Doctor Cornelius, when he flees his uncle Miraz. During the civil war, Caspian’s allies blow the horn at Aslan’s How, hoping for help.

Its call reaches the Pevensies in England and transports them from a railway station to the ruins of Cair Paravel. The horn is therefore Susan’s, not Caspian’s: Caspian merely inherits and uses it. The story also explains the dramatic time difference—only a year passes in England, while about 1,300 years have passed in Narnia.

The horn’s role is sometimes confused with the summons of Aslan, but it is the enchanted instrument that brings the Pevensies back. Susan later recognizes it as her own lost treasure.