A tauroctony was the depiction of Mithras ritually slaying a bull, that is a taurobolium. Mithra and the Bull: fresco from Dura Europos late 2ndâearly 3rd century Mithras was the central savior god of Mithraism, a syncretic Hellenistic mystery religion of male initiates that developed in the Eastern Mediterranean in the 2nd and 1st centuries BC and was practiced in the Roman Empire from... In ancient Rome, the taurobolium was the sacrifice of a bull, usually in connection with the worship of the Great Mother of the Gods, though not limited to it. ...
External Links
Mithra References Page
The Mithraic Mysteries by David Ulansey Scientific American, December 1989 (vol. 261, #6), pp. 130-135.
Mithraism by Roger Beck from the The Circle of Ancient Iranian Studies
Another more widely accepted interpretation takes its clue from the writer Porphyry, who recorded that the cave pictured in the tauroctony was intended to be "an image of the cosmos." According to this view, the cave depicted in that image may represent the "great cave" of the sky.
One of the central motifs of Mithraism is the tauroctony, the myth of sacrifice by Mithra of a sacred bull created by the supreme deity Ahura Mazda, which Mithra stabs to death in the cave, having been instructed to do so by a crow, sent from Ahura Mazda.
Further support for this theory is the presence of a lion and a cup in some depictions of the tauroctony: indeed Leo (a lion) and Aquarius ("the cup-bearer") were the constellations seen as the northernmost (summer solstice) and southernmost (winter solstice) positions in the sky during the age of Taurus.