Magnus Maximus and the Priscillianists analyses the Priscillianist controversy from the perspective of the imperial government, focusing on developments in imperial ideology and laws against sorcery, sexual immorality, and treason over the course of the fourth century in order to explain why Priscillian’s actions appeared so sinister to officials. A comparison of these laws to subcultural and religious activity in Hispania reveals diverse social norms and expectations often overlooked in scholarship. The interactions with and between officials during the controversy illustrate the methods of communication, varying personalities, interpersonal conflicts, and interconnectedness of those involved. These interactions collectively reveal that the Priscillianists exhibited the sort of ‘criminal’ behaviours that had preoccupied emperors since the First Tetrarchy, which were repeatedly dealt with through mass trials. The Priscillianist trials, when compared to earlier fourth-century mass trials, indicate a high degree of consistency in how emperors dealt with perceived bad behaviour in this period of tremendous changes. This book is essential for scholars and students of late antiquity, Roman history, and religious studies, particularly those interested in imperial governance, legal history, and the intersection of law and religion. It is also valuable for researchers examining subcultural dynamics and the broader social and political contexts of the fourth century.