Sword and Shadow, Book 6: The Rune Blades of Celi

For generations, the bold Celae have lived in exile, banished from their enchanted isle of Celi by the Somber Riders, whose leader, a dark sorcerer, cast an evil spell no trespasser can survive. But a glorious legend promises victory for the exiles. Two twins - princes of royal blood and secret birth - will take the Celae back home.