The Burning (Guardians of Ga'hoole, Book 6)

Soren and his band are sent to the mysterious Northern Kingdoms to gather allies and learn the art of war in preparation for the coming cataclysmic battle against the sinister Pure Ones. Meanwhile, in the Southern Kingdoms, St. Aggies has fallen to the Pure Ones and they are using its resources to plan a final invasion of The Great Ga'Hoole Tree. With the future of all Owldom in the balance, the parliament of Ga'Hoole must decide whether or not to join forces with the brutal Skench and Sporn and the scattered remnants of St. Aggies who remain faithful to them.