MYSTERY RELIGIONS. A term applied in the Greek, the Hellenistic, and the Roman world to the cult of certain deities that involved a private initiation ceremony and a reserved and secret ritual. They were probably vestiges of earlier religions, maintaining themselves as secret societies after the introduction of the Olympian and other Indo-European deities, and ending after what seems a common social pattern, by winning their way with the conquering people. The deities with whose worship the Greek “mysteries” were principally connected were Demeter, whose cult was organized into the ceremonials of Eleusis, and Dionysus, a predominantly female cult. The worship of Demeter and Dionysus appears to have been in origin a nature worship, with a ritual symbolizing death and resurrection in a seasonal sequence, and a spiritual reference of this natural pattern to the experience of the soul.