The Fallen Fortress (Forgotten Realms: The Cleric Quintet Book 4) by R A Salvatore

Cadderly and his friends have decided to take out the threat of Castle Trinity. Cadderly has started to grow in power as his faith in Denier grows. These new powers will be tested to there full on the journey as Aballister sends monsters to wipe them out. Unknown to his friends Cadderly plans to use the journey as an opportunity to destroy the evil device Ghearufu but there is only one way to do this. By immersing it in he breath of an Ancient Red Dragon. Can Cadderly defeat all the power of Castle Trinity in the base of their power and how will he deal with the revelation of who Aballister really is.

Cadderly has grown up and grown in faith and is now a likeable character he has come to terms with the realities of the world and what he must do to accomplish his goals. But the best part of the book for me is Pikel and his friendly snake, which is so funny.