Mithras: Taurobolism

The Cult of Mithras was a male-exclusive series of cults devoted to the Persian god Mithras. In the Persian pantheon, Mithras was a messenger god, but also a heroic god whose name means "contract" or "agreement". The time when this cult became Romanized is unclear, but with reasonable certainty it occurred sometime in the first century CE, some 2000 years after its Persian origins. However, it was not until the second and third centuries that the cult had a popular following. However, the cult was never able to surpass many other cults such as that of Isis or Christianity because of its strict male only membership.

A central image to Roman Mithraic cults was the myth of Mithras slaying the bull. Originally, this "cosmic bull" was slain as a sacrifice to give birth to the world. Creation leapt forth from the bull's blood, thus creating a heavily gendered creation myth. The artistic iconography usually involved Mithras plunging a dagger into the bull's throat while a dog lapped at the blood collecting at the bull's feet. In the Roman Mithraic cults, the bull represented masculinity, because of its strength and sexual power, as well as lunar and earthly forces; the slaying of the bull represented the triumph of male spirit over his animality. According to the Roman version of the Mithraic myth, from the god's slaying of the bull came wheat, wine, and the growth of herbs and plants.

Bull sacrifice was the centerpiece of the Roman cult as well as its progenitors, and eventually the ritual of the Taurobolium emerged in the Roman tradition. Taurobolium was a regeneration ritual in which the blood of the sacrificed bull was poured over an initiate, who lay in a pit underneath. This "baptism" in the bull's blood was meant to cleanse the moral faults of the initiate and to renew both his soul and his physical strength. The descent into the pit was seen as a sort of symbolic burial from which the initiate emerged reborn and purified--the blood itself was considered the purifying force.

Sources:

The Ecole Initiative: Mithraism

MITHRAISM: The Legacy of the Roman Empire's Final Pagan State Religion