Shadow Magic — James E. Wisher

The High Kingdom has known twenty years of peace. The true reason unknown to everyone save Sultan Vilos the First. At the height of The Crown War, Vilos made a deal with a powerful sorcerer. Vilos's reign would be secured in exchange for his first born daughter. The sorcerer promised to come for the princess on her eighteenth birthday. That day is today. The sorcerer is coming to claim his due and if he doesn't get it, all Hell is going to break loose.