Ghost Hunter by Michelle Paver

Her cry rips the souls from your marrow. With her spear she snares them. She devours them. Eostra truly is an eater of souls. Winter is coming. Souls' Night draws near. Eostra, the Eagle Owl Mage, holds the clans in the grip of terror. Torak must leave the Forest and seek her lair in the Mountain of Ghosts, while Renn faces an agonizing decision. Wolf, their faithful pack-brother, must overcome wrenching grief. And in the final battle against the forces of darkness, Torak will make the most shattering choice of all. Ghost Hunter, the final book in the Chronicles of Ancient Darkness series, draws the reader for the last time into the shadowy world of the deep past and brings Torak to the end of his incredible journey.