Blood: Book One
by Melissa Hayes
The first book of the KinSlayer Chronicles.
Damion is an Assassin, a Knife to be wielded by his master, killing whoever it is that must die until his soul is awash in so much blood he sees no way out of it. He knows nothing of human compassion any longer, is no longer able to feel anything but something he calls "the cold", a state of being that allows him to feel nothing at all.