overlord

A ruler of other rulers.

“The various tribal chieftains met each spring to elect an overlord that would lead them in time of war.”

In the English feudal system, a lord of a manor who had subinfeudated a particular manor, estate or fee, to a tenant.

“The tenant thenceforth owed to the overlord one of a variety of services, usually military service or serjeanty, depending on which form of tenure the estate was held under.”

Anyone with overarching power or authority in a given domain.

“The crusty old professor was overlord of the history department, and few dared to cross his will.”

To rule over; to domineer.