Spirit Ascendancy: Book 3 of The Gateway Trilogy - E. E. Holmes - Bog

In the wake of their terrifying escape from Fairhaven Hall, sisters Jess and Hannah Ballard find themselves on the run, pursued by the two most powerful groups in the history of the spirit world. On one side, the Durupinen, determined to capture the girls and prevent their role in an ancient prophecy that promises to destroy them and unleash the spirit hordes on the earth. On the other side, the Necromancers, ancient enemies of the Durupinen, hellbent on bringing the same prophecy to fruition. When the girls are betrayed and one of them falls into the Necromancers' hands, both face decisions with cataclysmic consequences.