Charn is the fictional kingdom ruled by Queen Jadis in C.S. Lewis’s The Magician’s Nephew.
The novel presents Charn as an abandoned world whose last ruler is Jadis. Digory Kirke and Polly Plummer reach it through magical travel, and Digory awakens Jadis by ringing a bell in a ruined palace. Their actions eventually connect Charn’s catastrophe with the creation of Narnia.
Charn is not another name for Narnia. It is a separate world, and its destroyed civilization provides one of the book’s warnings about pride, power, and destructive ambition. Jadis later becomes the White Witch in the Narnian story.
Archenland and Calormen are countries within the wider Narnian world. Their presence in other books can make the names seem interchangeable, but Charn belongs specifically to the earlier world visited in The Magician’s Nephew.