1. In Ancient Greece, one who gave preparatory instruction to candidates for the initiation into the Eleusinian or other mysteries; a hierophant: A mystagogue was one who introduced someone to religious mysteries, or was a teacher of mystical doctrines.
2. One who keeps church relics and presents them to the public: The priest was a mystagogue who had a great collection of church antiquities that were on display in a show case for interested people to view.