The Collaborative International Dictionary of English v.0.48:

Hierophant \Hi*er"o*phant\ (h[-i]*[e^]r"[-o]*fant or
   h[imac]"[~e]r; 277), n. [L. hierophanta, hierophantes, Gr.
   "ierofa`nths; "iero`s sacred + fai`nein to show, make known:
   cf. F. hi['e]rophante.]
   The presiding priest who initiated candidates at the
   Eleusinian mysteries; hence, 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.

   Syn: mystagogue. [1913 Webster]

   2. an advocate or spokesperson.
      [PJC]