Nightwalker: The First Dark Days Novel (Dark Days Series, 1, Band 1)

For centuries Mira has been a nightwalker—an unstoppable enforcer for a mysterious organization that manipulates earth-shaking events from the darkest shadows. But elemental mastery over fire sets her apart from others of her night-prowling breed . . . and may be all that prevents her doom.
The foe she now faces is human: the vampire hunter called Danaus, who has already destroyed so many undead. For Mira, the time has come to hunt . . . or be hunted.