The battle for Crystal Castle : the thirteenth adventure in the Kingdom of Fantasy / Geronimo Stilton ; cover by Danilo Barozzi ; illustrations by Silvia Bigolin, Carla Bebernardi, Ivan Bigarella, Alessandro Muscillo, and Danilo Barozzi and Christian Aliprandi ; translated by Julia Heim.
The Harmony Stone has been stolen from the Crystal Castle, and without it the Kingdom of Fantasy is vulnerable to an ancient enemy, The Invisible Army; Geronimo, together with Queen Blossom's daughter, Winglet, embarks on a mission to find the ancient crown which will defeat the Invisible Army and restore harmony to the empire--but they must make it back to the Crystal Castle before it is overwhelmed by the enemy.