Secret rituals of pagan religions taught and known only to initiates who had developed a higher spirituality. Such mysteries were kept from the popular worshipers, and the initiates took a binding oath of secrecy. This is why even today the knowledge of these mysteries is partly conjectural.
The typical mystery cults were those of Eleusis in Greece in the 15th century BC, which may have part of their origins in the mystery religions of ancient Egypt and the mysteries of Mithras, a Persian deity. Traces of Mithraism still exist in Britain. Many present secret societies claim their ritual descend from ancient traditions. A.G.H.