Dormaine G 
The Battle [EPUB ebook] 

Connor has trained and shed blood to protect Earth. Her enemies want war, and Connor’s blood is the key to the survival of Ether’s last descendant.
Against her friends’ council, Connor joins forces with her former adversary, Ronin. And as the danger intensifies, so does their bond.
For Ronin, the only way to survive is to kill. Planning to overthrow his father with Connor’s help, he brings her to the very definition of hell: his world.
Despite his unyielding, merciless ways, Connor has started to thaw his frozen heart. But how far will Connor need to go to survive?