The Lost Prince (Dark Border, Vol. 1)

Were it not for the awesome power of the Hasturs, the creatures contained by the dark border would overrun mankind. As humans reeled from the constant onslaught only to rebound, the darkness searched for another path to victory. It stole a princeling and raised him in Shadow, teaching him what no human had ever learned. It taught him how to command the living and the dead, how to usurp his brother's throne through magic, and how to turn the humans against themselves. And then it sent him home.