Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† mystăgōgus, i, m., = μυσταγωγός, one who conducts a person through secret and sacred places as a guide, an initiator, a mystagogue, Cic. Verr. 2, 4, 59, § 132.
Trop.: amicitiae meae, te mystagogo usus, accessit, the founder, Symm. Ep. 5, 64.