mystagogue
A person who prepares an initiate for entry into a mystery cult, or who teaches mystical doctrines.
There is an overruling destiny above us, though not in the sense in which it was viewed by that wretched man, who, beguiled by some foreign mystagogue, used the awful word as the ready apology for whatever he chose to do—we must examine the packet.
Where it comes from
From Latin mystagōgus, Ancient Greek μυσταγωγός (mustagōgós). By surface analysis, mystic + -agogue.
Adapted from the Wiktionary entry mystagogue (CC BY-SA 4.0).