Casteron, the sequel to Asherill, finds Marta and her brother Brennan still searching for answers as their past and present collide. Their search has led them into the country to the north of Asherill; its sworn enemy, Casteron. Fleeing from the raiders' brutality, many of the residents of the beleaguered country have sought refuge there, and the siblings find themselves shuttled into a refugee camp where the best interests of the refugees does not seem to be the priority. Between rescuing the displaced citizens of Asherill and trying to discover the true reasons behind the strange recent events, friendships are formed, alliances are made and an enemy is discovered who proves to be more powerful and ruthless than they could have imagined.