The Reaper’s Soul by A.M. Wilder

Two sisters, broken by loss and betrayal, must find a way to move past their fears and doubts to defeat the creature who has destroyed their lives.
In Brooke's quest to find and kill the Reapers, she is joined by Alaric, a healer haunted by his inability to save his patients, and Ian, an ex-soldier struggling to put his past behind him. The sorceress Alonda is the only person who has the power to destroy the Reapers, but where do her loyalties truly lie? With humanity, or with the bloodthirsty Reapers? If Brooke, Ian, and Alaric manage to find her, more might be saved from Vivian's fate. But there are many perils to be faced on their journey, apart from the Reapers. A malevolent band of vigilantes, and the legendary Forest of the Night stand between them and their last hope of defeating the Reapers forever.
 
- Goodreads Summary