From Whence Come These Demon Children: The Third Expedition of the Six Fingers: The Six Fingers Series, Book 3 (Unabridged‪)‬

The Six Fingers return to Northem with a powerful, magical artifact known as the Azure Font. They mount it atop the ancient Faellic tower, but have little idea of what comes next. When the Red Lady senses something "truly evil" rising in the south, they embark on their third expedition. It takes them across the nightmarish Sea of Spires and into the heart of Atmaa, the last kingdom untouched by the Askerati hordes. As they discover, something worse than child-burning zealots has awakened.