The Evertree by Marie Lu

Spirit animals bk 7. Scholastic Australia, 2015. ISBN 9781743620045
Finally, the last in the Spirit animals series where the fate of Erdas will be revealed, not to mention that of the amazing four young protagonists who have endured so much since they discovered their spirit animals were the famous Fallen Ones. As the series ends there is an even stronger message that the survival of our world depends on a balance between man, the animals and the environment.
The Greencloaks have gathered their allies for a final battle as Conor is beset by visions of a final confrontation with Kovo and the Conquerors. The outcome is uncertain and there is fear that their spirit animals may not survive this battle. Melin is still imprisoned by the power of Gerathon whilst still hoping that her friends will succeed in their quest.
On their way to stop Shane setting Kovo free, they travel through the dry devastated and desolate lands of Stetriol, all the time battling the strange weather and armies of Conquerors. They are also hoping also to find Tellun the Elk, last of the Great Beasts who has yet to surrender his talisman, and enlist his help.
Too late to stop Kovo escaping, they head to The Evertree, the legendary place where all life began, for a last stand against the power hungry Kovo and his allies Gerathon and Halawir. With all the great beasts present and willing to save Erdas at all costs it is up to Tellun and the children to succeed in their final battle.
As with the other books in the series there is hardship, bloody battles, death and destruction interspersed with moments of tenderness and beauty as the power of friendship helps overcome even the darkness of the Bile. The final act of forgiveness in letting Shane escape is not without its reward with a spinoff three part novella series by Nick Eliopulos in e-book form available, telling his side of the story.
Sue Keane