The Call of Earth — Orson Scott Card

As Harmony's Oversoul grows weaker, a great warrior has arisen to challenge its bans. His name is Moozh, and he has won control of an army using forbidden technology. Now he is aiming his soldiers at the city of Basilica, that strong fortress above the Plain.

Basilica remains in turmoil. Wetchik and his sons are not strong enough to stop an army. Can Rasa and her allies defeat him through intrigue, or will Moozh take the city and all who are in it?