Archdevils

The Archdevils, also known as the Prime Devils or Ascended Devils, were the eight most powerful devils in the Infernal Plane. Each was given their power by Asmodeus and a layer of the Nine Hells to rule over. These positions fluctuated with time, as Asmodeus gained and lost faith in one devil or another, and as backstabbing occurred within the ranks. It was not uncommon for an Archdevil to be betrayed by one of their servants and slain, at which point Asmodeus would promote the betrayer to Archdevil for their bloodthirsty determination.

The Archdevils could reach near-Lesser God levels of power, though this varied and fluctuated depending on their standing with Asmodeus.

Hierarchy
The Archdevils were typically arranged in power and prestige by the layer they presided over. However, their power and importance were not necessarily absolute, as many occupied pivotal roles necessary to the status quo of reality (Zariel's position in the outermost layer of Avernus did not reflect her immense importance as the High Commander of the Nine Hells).

Avernus

 * Zariel: Archduchess of the First Layer, and the High General of the Nine Hells. A fallen angel who was granted her position by Asmodeus under the promise she could one day lead the armies of the Nine Hells against the gods, so that she could claim her revenge.
 * Bel: The High General of Avernus.
 * Arthos: The Field Marshal of Avernus and a Hell Knight who served as the primary servant of Bel and Zariel.

Dis

 * Dispater: Archduke of the Second Layer. A particularly cowardly and paranoid fiend who preferred to act through proxies.
 * Lilis: Consort to Dispater, and his primary advisor.

Minauros

 * Mammon: The corpulent Archduke of the Third Layer. The embodiment of greed amongst the Archdevils, known to bankroll the activities of many beings.
 * Bael: The High General of Minauros and Mammon's enforcer.

Phlegethos

 * Fierna: Archduchess of Phlegethos. A fiery and beautiful fiend with a penchant for seducing and corrupting mortals, especially paladins and clerics of good-aligned gods.
 * Belial: The former archduke of Phlegethos and the father of Fierna. Voluntarily gave up rule for his daughter, but still serves as her primary advisor, granting him a massive amount of power and influence.

Stygia

 * Levistus: The Archduke of the Fifth Layer, imprisoned in a massive iceberg for all eternity as punishment for a previous slight against Asmodeus. Oddly enough, Asmodeus allowed him to retain his position as Archduke. Acts by telepathically communicating with his underlings, primarily Agares.
 * Agares: A Duke of Stygia, most powerful among the devils in that Layer and seemingly favored by Levistus.

Malbolge

 * Glasya: The Archduchess of the Sixth Layer and daughter of Asmodeus. Charged with overseeing the Erinyes and their activities.

Maladomini

 * Baalzebul: Archduke of the Seventh Layer, also known as "The Lord of the Flies."
 * Zepar: A Duke and General, twin of Abigor.
 * Abigor: A Duke and General, twin of Zepar.

Cania

 * Savitar: Archduke of the Eight Layer. Deposed the previous Archduke, Mephistopheles, after aiding him and eventually betraying him in a plot to kill and replace Asmodeus.
 * Irene: A powerful Erinyes and High General of Cania. Wife of Zalphas.
 * Zalphas: A fiend who was once a great soldier in life, turned into a fiend by his love for his wife. High General of Cania.