heresiarch

Borrowed from French hérésiarque, from Ecclesiastical Latin haeresiarcha (or directly from the Latin word), from ecclesiastical Medieval Greek αἱρεσιάρχης (hairesiárkhēs, “leader of a sect”), from Ancient Greek αἵρεσῐς (haíresĭs, “heresy”) + -ᾰ́ρχης (-ắrkhēs, “leader, ruler”), corresponding to heresy +‎ -arch.