From The Weird Review: The White People:

Mysteries, from the Greek word muein, to shut the mouth, & mustes, an initiate, is a term for what is secret or concealed in a religious context. Devotees in the ancient world were brought into relationship with their gods by means of participation in the rites of Mysteries, of which the Graeco-Roman are the most familiar: those of Demeter & her daughter Kore, or Persephone (Eleusinian), & of Dionysus (Dionysian). Others include those of the Phrygian gods Attis & Cybele, & the Persian god Mithras. They are all characterized by stages of preparation & initiation. Common elements of preparation are vows of secrecy & deterrent formulae, purifications or baptisms, sacrifices, pilgrimages, self-mortification, robing, crowning, & enthroning, etc.