Ramandu is a star at rest; one who has become too old to dance the Great Dance, and has come to the Island for rest and rejuvenation. Everyday he and his daughter greet the day with a song, and a bird flies by and places a bright berry in his mouth, which renews him until he is ready to rejoin the skies. It is not known how long the rejuvenation process takes, but it is implied that each day spent on the Island subtracts one day from the star's age.
When Caspian and his crew sail to Ramandu's Island in search for the remaining three missing Lords, they find them there under a deep enchantment. He presses Caspian to make a decision about sailing East in order to break the enchantment, and explains to him that it cannot be done unless all of his crew is ready and willing to do so. He generously offers to allow any crew members who do not wish to go permission to spend the winter on his Island, and feast every day. He also places an enchantment of rest on the broken Lord Rhoop, allowing him to experience refreshment until Caspian's return.
When Caspian returned from the East having broken the enchantment, Ramandu's daughter sailed back to Narnia with him, having fallen in love with the King.
Ramandu is not mentioned after that, and it is not known if he joined the Great Dance once more before the end of Narnia.