he·re·si·arch 
(hə-rēzē-ärk′, hĕrĭ-sē-)
(hə-rēzē-ärk′, hĕrĭ-sē-)n.
One who originates or is the chief proponent of a heresy or heretical movement.
[Late Latin haeresiarcha, from Late Greek hairesiarkhēs : Greek hairesis, sect; see HERESY + Greek -arkhēs, -arch.]