"The Chaos Curse" by R.A. Salvatore (Forgotten Realms; The Cleric Quintet, Book V)

The prequel series to "The Ghost King" comes to an explosive end!

Cadderly journeys home to the Edificant Library, hoping to rebuild his shattered life--but the chaos curse has one last surprise in store for him. Failure means the loss of his beloved Danica, success might usher in a new era for the followers of Denier.