The Dark Cage: A Young Adult Urban Fantasy Novel. The Soulless War Trilogy, #3

Powers of life and death are hard to resist... Doctor Zero has been defeated, but there's just one problem-before his death, he managed to turn Riley Stark soulless with his serum. Protected by the Purity Crystal, she's now able to feel emotions, but the Sentinels and her family and friends have slowly turned their backs on her. While Riley tries to prove she's still the same girl, an old soulless legend called the Cardinal rises.
Thought to be a soulless God with the power to control the Quintessence-the land of souls, better known as the afterlife-everyone fears he's returned to take over the world. As Riley's former best friend returns, he brings an army with him called the Darkhunters who are intent on killing all the soulless for good. When he discovers Riley's transformation, he kidnaps her and creates a radioactive bomb that can destroy the soulless. With friends becoming enemies and an old soulless God waiting in the shadows, Riley will have to fight to save the world and control her new power before she loses it all.