Child of the Ghosts by Jonathan Moeller
When her life is torn apart by sorcery and murder, young Caina Amalas joins the mysterious Ghosts, the legendary spies and assassins of the Emperor of Nighmar. She learns the secrets of disguise and stealth, of assassination and infiltration.
But even that might not be enough to save her.
For the evil that destroyed her family seeks to devour the entire world…