Catherine Fisher 
Interrex: Book of the Crow 2 [EPUB ebook] 

Having tapped into the Crow, the Order’s legendary powerhouse, Galen is charged with a force beyond anything he, or his apprentice, Raffi have ever known. And when, during the ritual ceremony on the night of Flainsdeath, Galen receives a message from the makers urging him to find the Interrex — the child of the last great Emperor — Galen knows that the Keepers are tantalisingly close to the brink of a revolution. Meanwhile, Gary is struggling to come to terms with her past, her identity and the mystery of how she became a member of the Watch.