The Forsaken: Wraith (The Forsaken, #1)

In one night of snow and blood, Alena Athscar lost her family, her home and her name. Raised in secret and trained by the Guild of thieves and assassins, the lost girl returns to the world as Slayer, a hunter of monsters. But it is not just beasts and demons she must face.
The sorcerers of the Sacred hold dominion over the realms of Centuros, forcibly inducting any they chose and punishing all who deny them. They are Slayer's new employer, yet she possesses the very thing they seek and will stop at nothing to claim.