Geronimo Stilton: The Battle for Crystal Castle — the Kingdom of Fantasy #13

Geronimo Stilton is drawn back into the magical Kingdom of Fantasy when the Harmony Stone is stolen from the Crystal Castle, leaving the empire vulnerable to the looming threat of the Invisible Army. With time running out, Geronimo and allies must find an ancient crown to restore harmony and prevent the Castle’s fall — a high-stakes quest full of magic, dragons, and adventure.