Fortress of Fire - The Cloud Warrior Saga, #4

The barrier has fallen. The king is gone. Tan has secured the artifact, but now the Fortress of Fire in Incendin burns more brightly than it has in a generation. To master his connection to the elementals, Tan needs to rediscover knowledge about the elemental power that has been lost for centuries. When the draasin bonded to him is injured, Tan must rely on everything he's learned to save him and discovers a new threat to the kingdoms more powerful than anything he's ever faced.