Although it would appear in studies of late antique ecclesiastical authority and power that scholars have covered everything, an important aspect of the urban bishop has long been neglected: his role as demonologist and exorcist. When the emperor Constantine made Christianity the official religion of the realm, bishops and priests everywhere struggled  to “Christianize” the urban spaces still dominated by Greco-Roman monuments and festivals. During this period of upheaval, when congregants seemingly attended everything but their own “orthodox” church, many ecclesiastical leaders began simultaneously to promote aggressive and insidious depictions of the demonic. In City of Demons, Dayna S. Kalleres investigates this developing discourse and the church-sponsored rituals that went along with it, showing how shifting ecclesiastical demonologies and evolving practices of exorcism profoundly shaped Christian life in the fourth century.