The priest (rex Nemoriensis) at the grove of Diana, the Goddess of the Wild Wood at Nemi, was a runaway slave. What was unusual is that this slave became the priest by killing his predecessor in combat. Virbius, Diana’s Consort, is said to have begun this custom. The God of the Month: Diana
What most people know about this ritual sacrifice comes from James Frazer and his work, “The Golden Bough.” (The title refers to the challenger breaking a tree bough to announce his challenge.) Frazer theorized that it was a fertility rite culminating with the sacrifice of the sacred king.
Roman sources do not support Frazer’s theory. In fact, they found this human sacrifice to be both problematic and barbaric. Since it was tied to the Gods, they struggled with what to do about this ancient custom. How could they end it and still maintain the Pax Deorum (Peace of the Gods)? For the Romans, the purpose of any sacrifice was a gift to the Gods, Heroes, and the Dead.
The most extreme sacrifice is for the Romans was the devotio. A Roman general facing a major loss in battle would offer his life. In a complex ritual, he dedicated himself and the enemy to Tellus and the Manes as the Gods of the Underworld. His death in battle would oblige the Gods to take the lives of the enemy. If he survived and won, he would bury a seven foot (2.13 meters) model of himself instead.
The Romans did practice human sacrifice on extreme occasions. After several threats of destruction to Rome, the Senate consulted the Sibylline Books for advice. They buried a Gaul couple and a Greek couple alive to fend off impending doom. Then in 97 BCE, the Roman Senate outlawed human sacrifice all together, calling it a “most un-Roman ritual.”
Human sacrifice has been problematic for Polytheistic cultures. Each has grappled with the practice. For the Romans, after the reforms of Numa Pompilius (Second King of Rome), various substitutions for humans were made.