Samuel’s Life of Barsauma, a little-studied, late fifth-century Syriac text, commemorates the ascetic career of a nasty saint. One of the most noticeable features of this monastic hagiography is the high degree and diversity of violence: Barsauma is frequently portrayed as the victim of violence by his adversaries and the perpetrator of violence against his adversaries. Yet, the Life of Barsauma stands out from other late ancient monastic hagiographies because of its enthusiastic depiction of the saint’s lethality. According to Samuel, Barsauma uses his curse to kill an array of individuals, and the mere presence of him and his disciples leads to the mass deaths of Jews gathered in Jerusalem. For most late ancient hagiographers, a saint’s performance of violence was something to be downplayed or specifically rationalized, and rarely if ever would a saint’s performance of holy violence lead to the death of one person, let alone many people. The Life of Barsauma’s deviation from contemporary hagiographical convention compels this article’s investigation into the meaning that Samuel hoped to communicate through his thorough depiction of a lethally violent saint. I argue that Samuel’s Life constitutes the literary amplification of a memory about the historical Barsauma, and an exhortation for the monks of Barsauma’s monastery to imitate him with similarly violent actions. In the end, Samuel’s defies the conventions of monastic hagiography in order to authorize readers to perform their own acts of violence as they construct and police the monastic community’s sectarian boundaries.