Archfiend

An archfiend was a particularly powerful fiend, usually a demon lord or an archdevil. An archfiend typically ruled a layer of the Abyss or the Nine Hells. Some archfiends were worshiped as gods, while others preferred to discreetly accrue power.

Demon Lords
Demon lord was a self-proclaimed title used by the most powerful demons of the Abyss. Though there were no formal criteria for the title, most demon lords were extremely powerful, controlled at least one Abyssal layer, and commanded armies of lesser demons. Each of them had a unique set of powers and abilities. The most powerful demon lords sometimes called themselves demon princes. Prominent demon lords included Demogorgon, Orcus, and Graz'zt.

Archdevils
Archdevils were the greatest of devils, and the archdukes of the Nine Hells. As befitting their kind, their position was strictly dictated by the hierarchy of the Nine Hells. Only nine archdukes ruled at any given time, one for each layer of Baator. Deposed or banished archdukes were also referred to as archdevils. Prominent archdevils included Asmodeus, Zariel, and Mephistopheles.