Lords of the Nine
The Lords of the Nine are the rulers of the Nine Hells of Baator, consisting of Asmodeus and the eight stewards whom he charges with governing the upper eight layers of Hell as viceroys. They are the greatest of the archdevils, and reign their layers with virtual impunity, so long as they maintain order and execute the will of Asmodeus.
The politics of Hell is complicated, to say the least, and thus it is difficult to keep track of who is in power; for example, Zariel and Bel overthrow each other every other Tuesday, leaving us with conflicting reports as to who reigns in Avernus at any given time. However, some of the Lords of the Nine about whose status there is widespread agreement among scholars are Dispater (Lord of the Second), Glasya (Lady of the Sixth); and Asmodeus (Lord of the Ninth).