Hierophant
Hierophant (hi*er"o*fant or hī"ẽr; 277) , noun
[Latin hierophanta, hierophantes, Greek "ierofa`nths; "iero`s sacred + fai`nein to show, make known: compare French hiérophante.]
The presiding priest who initiated candidates at the Eleusinian mysteries;
one who teaches the mysteries and duties of a religion or an arcane discipline; an expositor; as, In his television series “Cosmos”, Carl Sagan became the foremost hierophant of modern cosmology.. — Abp. Potter
2.
an advocate or spokesperson.