Anne Perry 
Come Armageddon 

After half a millennium, Tathea prepares for the final battle For five hundred years, Tathea has lain asleep, imprisoned in the forest. Once the Empress of Shinabar, she was pushed out of power when a coup took her husband’s life—a tragedy that led to a miracle. While roaming the wasteland, she learned of the unending battle between good and evil, and a book that could stop the demon Asmodeus forevermore.   It takes centuries, but at last the world is ready for the final battle—the Armageddon that will purge Tathea’s kingdom of evil. The coming of the war is marked by the birth of a child, Sadokhar, who will lead God’s armies into the fray. A battle is looming, and it’s up to Tathea to prepare Sadokhar for Armageddon . . .  Come Armageddon is the second book in the Tathea series, but you may enjoy reading the series in any order.