Book 3 of The Kinshield Saga

Having banished the demon released from its prison by his defeated nemesis Ravenkind, Gavin Kinshield faces new challenges: a magical barrage by Ravenkind's grieving mother and an age-old mystery whose time has come to be revealed.

A former member of an elite battlers' guild, Cirang Deathsblade has a dark past. She sits in gaol, awaiting the new king's sentence for her terrible crimes... but she's not who he thinks she is. 

In exchange for leniency, Cirang leads Gavin to a centuries-old, hidden journal that holds the secrets of ancient kings and a magical wellspring with its own dark past... and an even more terrible future.