Ascension of the Warlock (Book 4 of the Death Incarnate Saga)
After another near-death experience, Cage is taught in the ancient ways by those ancient enough to remember. Blood and Battle are what is needed and Daku won't give Cage much rest till his power finally awakens. It is all Cage can do to not enjoy the rush of combat.
But not everyone is comfortable and will try to take him out. Still, a new surprise awaits him when he goes home, one that rocks.