Kybele was one of the most important Asian mother goddesses, probably originating as a mountain goddess, who became equated with the Greek goddesses Rhea and Demeter. According to legend Zeus raped her and she bore a monstrous son Agdistis. Her consort was Attis who was unfaithful to her, and in remorse, after Kybele's discovery of his transgression, castrated himself under a pine tree and bled to death.
About 204 BC the black stone by which she was personified in Pessinus (Phrygia) was carried to Rome and installed in the Temple of Victories on the Palatine as Cybele Magna Mater; thus fulfilling a prophecy that if the "great mother" was brought to Rome, the war with the invader Hannibal would be won. She is frequently depicted riding in a chariot drawn by panthers or lions and is accompanied by frenzied dancers or Konybantes. She was invoked in the three-day festival commencing with mourning (tristia) followed by joy (hiralia) in the spring during which her emasculated priests, the galloi, gashed themselves with knives. Her attributes included the key, mirror, and pomegranate. A.G.H.
Jordan, Michael, Encyclopedia of Gods, New York, Facts On File, Inc. 1993, p. 141