mystagogue (n.)

"person who initiates into mysteries," 1550s, from Latin mystagogus "a guide to the mysteries," from Greek mystagōgos, from mystēs "one initiated into the mysteries" (see mystery (n.1)) + agōgos "leading, a leader," from agein "to lead" (from PIE root *ag- "to drive, draw out or forth, move"). Related: Mystagogic; mystagogical.