What is "tauroctony"

n. A depiction of Mithras killing a bull.

Tauroctony is a modern name given to the central cult reliefs of the Roman Mithraic Mysteries. The imagery depicts Mithras killing a bull, hence the name tauroctony after the Greek word tauroktonos (ταυροκτόνος, "bull killing").

Despite the name, the scene is symbolic, and there is no evidence that patrons of the Roman cult ever performed such a rite. Like all Greco-Roman mysteries, the Mithraic Mysteries was limited to initiates, and there is very little known about the cult's beliefs or practices. However, several images of the bull include a dorsuale ribbon or blanket, which was a Roman convention to identify a sacrificial animal, so it is fairly certain that the killing of the bull represents a sacrificial act. And, because the main bull-killing scene is often accompanied by explicit depictions of the sun, moon, and stars, it is also fairly certain that the scene has astrological connotations. But despite dozens of theories on the subject, none has received widespread acceptance. While the basic bull-killing image appears to have been adopted from a similar depiction of Nike, and it is certain that the bull-killing symbolism and the ancillary elements together tell a story (i.e. the cult myth, the cult's mystery), what that story was is only known to Mithraic initiates. Following several decades of increasingly convoluted theories, Mithraic scholarship is now generally disinclined to speculation.

The tauroctony should not be confused with a " taurobolium", which was an actual bull-killing cult act performed by initiates of the Mysteries of Magna Mater, and has nothing to do with the Mithraic Mysteries. "There is no evidence that [initiates of the Mithraic mysteries] ever performed such a rite [i.e. a real bull killing], and a priori considerations suggest that a mithraeum – any mithraeum – would be a most impractical place to attempt it."