The Spirit War is the fourth volume in Rachel Aaron’s Legend of Eli Monpress series, released in June 2012, which focuses on the fallout from a massive invasion led by the Immortal Empress. The story centers on Josef, who is revealed to be a prince, while Eli must navigate the consequences of his past decisions to protect his team and confront the invading forces. You can find the book at Goodreads or Amazon . The Legend of Eli Monpress #4 - The Spirit War - Goodreads