Mystery cults

Mystery religions, sacred mysteries or simply mysteries, were religious schools of the Greco-Roman world for which participation was reserved to initiates (mystai). The main characterization of this religion is the secrecy associated with the particulars of the initiation and the ritual practice, which may not be revealed to outsiders. The most famous mysteries of Greco-Roman antiquity were the Eleusinian Mysteries, which were of considerable antiquity and predated the Greek Dark Ages. The mystery schools flourished in Late Antiquity; Julian the Apostate in the mid 4th century is known to have been initiated into three distinct mystery schools — most notably the mithraists. Due to the secret nature of the school, and because the mystery religions of Late Antiquity were persecuted by the Christian Roman Empire from the 4th century, the details of these religious practices are derived from descriptions, imagery and cross-cultural studies. "Because of this element of secrecy, we are ill-informed as to the beliefs and practices of the various mystery faiths. We know that they had a general likeness to one another".

Justin Martyr in the 2nd century explicitly noted and identified them as "demonic imitations" of the true faith, and that "the devils, in imitation of what was said by Moses, asserted that Proserpine was the daughter of Jupiter, and instigated the people to set up an image of her under the name of Kore" (First Apology). Through the 1st to 4th century, Christianity stood in direct competition for adherents with the mystery schools, insofar as the "mystery schools too were an intrinsic element of the non-Jewish horizon of the reception of the Christian message". They too were "embraced by the process of the inculturation of Christianity in its initial phase", and they made "their own contribution to this process". In Klauck and McNeil's opinion, "the Christian doctrine of the sacraments, in the form in which we know it, would not have arisen without this interaction; and Christology too understood how to 'take up' the mythical inheritance, purifying it and elevating it".

...
Wikipedia