Archdevil

The archdevils were the rulers of the Nine Hells. They were also called the Lords of the Nine, the Archdukes of Hell, and the Lords of Hell. They each controlled one of the plane's nine layers and were the most powerful and highest-ranking devils. Unlike the chaotic evil demon lords of the Abyss, the Lords of the Nine (and all the baatezu of the Hells for that matter) were arranged in a strict hierarchy. The lord of the first layer had the lowest rank of the nine archdevils, while the lord of the ninth layer had the highest rank. While the demons of the Abyss answered only to their own basic instincts, every single devil, at least in theory, answered to the Lord of the Ninth, Asmodeus.

Each archduke was a unique devil of immense power and influence, with his own resources: military, magical, and political, to rely on in the endless scheming that characterizes devilish politics.

The Lords of the Nine
The Lords of the Nine were the archdukes of Baator, each one a ruler of an entire layer. The archdukes had power over all devils, and were served by lesser archdevils.

Archdevils of Avernus
The Lord of the First and commander of the diabolical armies in the Blood War, Zariel was a fallen angel and had been appointed to her archdukedom by Asmodeus himself. A general under the command of Zariel and a former archduke himself. A duke and general in Avernus, he was a vassal of Tiamat at one point. A general of Avernus and vassal of Tiamat alongside Amduscias.
 * Zariel :
 * Bel :
 * Amduscias :
 * Malphas :

Archdevils of Dis
The Lord of the Second, Dispater rarely left his Iron Tower due to his extreme paranoia. The loyal consort of Dispater. Although not very powerful personally, Titivilus was Dispater's closest adviser. A duke of Dis in the service of Dispater. A vassal of Dispater who meted out vengeance on those who dared defy his master. The loyal provost of Dispater. A duke of Dis. A duke of Dis.
 * Dispater :
 * Lilis :
 * Titivilus :
 * Bitru :
 * Arioch :
 * Biffant :
 * Merodach :
 * Alocer :

Archdevils of Minauros
The ruler of Minauros and patron of greed. A powerful general in the service of Mammon. The cautious seneschal of Mammon. A duke of Minauros. A duke of Minauros.
 * Mammon :
 * Bael :
 * Focalor :
 * Caarcrinolaas :
 * Melchon :

Archdevils of Phlegethos
The official Lord of the Fourth. The father of Fierna as well as her predecessor, Belial was in part the power behind the throne of Phlegethos. An archdevil who served Belial as legate. A duke of Phelgethos who served Belial. A duke of Phlegethos who served Belial. A duke of Phlegethos who served Belial.
 * Fierna :
 * Belial :
 * Chamo :
 * Balan :
 * Bathym :
 * Gaziel :

Archdevils of Stygia
The Lord of the Fifth, Levistus, was imprisoned in an iceberg by Asmodeus for past crimes. He was therefore forced to telepathically relay instructions to his minions, even as he also had to deal with his predecessor's continued existence. The deposed Lord of the Fifth, Geryon was a savage archdevil who sought to reclaim his former position. The consort of Geryon. The bailiff of Geryon. An archdevil who served Geryon as a magistrate. A vassal and former duke in the service of Geryon. A vassal and duke under Geryon's reign. The weakest duke who served Geryon.
 * Levistus :
 * Geryon :
 * Cozbi :
 * Gorson :
 * Herodias :
 * Amon :
 * Agares :
 * Machalas :

Archdevils of Malbolge
The daughter of Asmodeus, Glasya was the Lord of the Sixth.
 * Glasya :

Archdevils of Maladomini
Also called the Lord of Lies, the Lord of the Seventh was the repulsive fallen angel who was once called Triel. The quiet consort of Baalzebul. The herald of Baalzebul. The marshal of Maladomini. A duke of Maladomini. A duke of Maladomini.
 * Baalzebul :
 * Baftis :
 * Neabaz :
 * Barbatos :
 * Abigor :
 * Zepar :

Archdevils of Cania
The Lord of Cania, Mephistopheles was always plotting against Asmodeus. Consort of Mephistopheles and quite possibly the reason why the Lord of the Eighth was not demoted. A duke of Cania and powerful general who loyally served Mephistopheles. The justiciar of Cania. The steward of Cania. An archdevil who served Mephistopheles as chamberlain. A powerful duke and vassal of Mephistopheles.
 * Mephistopheles :
 * Baalphegor :
 * Hutijin :
 * Bele :
 * Adonides :
 * Barbas :
 * Bifrons :

Archdevils of Nessus
The Lord of the Ninth and King of the Hells, Asmodeus was deity in his own right. The Chancellor of Hell and Keeper of Records, Adramalech answered only to Asmodeus. The dreaded Inquisitor of Hell. A duke of Nessus. A duke of Nessus. A duke of Nessus. A duke of Nessus and former Lord of the Eighth. A duke in the service of Asmodeus.
 * Asmodeus :
 * Adramalech :
 * Phongor :
 * Buer :
 * Bune :
 * Morax :
 * Rimmon :
 * Zagum :

Other Archdevils
Of course, due to the nature of politics in the Nine Hells, archdevils wound up exiled or dead at various times. Some exiles remained in the Nine Hells (such as Geryon and his court, listed above), while others were forced to leave completely.

Additionally, the dragon goddess Tiamat spent some time as an archdevil after her Untheric aspect was killed. She was ruler of Avernus during her time there.

Exiled Archdevils
Some archdevils, former archdukes, were exiled or imprisoned, but survived. These included: A once-powerful archdevil who left the Hells for unknown reason. Also called The Branded King, Malkizid was a fallen solar who became an archdevil. He appeared similar to a solar, but with white skin, gray feathered wings, and bird-like talons on his hands and feet. He was exiled after earning Asmodeus' disfavor, and went to reside in the Blood Rift. An archdevil exiled by Asmodeus. Former Lord of the Sixth, Moloch was exiled for rebellion by Asmodeus. The various vassals and servitors of Moloch, now presumably deposed and possibly exiled as well, included his consort Lilith, his legate Tartach, and the tribune Bileth.
 * Gargauth :
 * Malkizid :
 * Nergal :
 * Moloch :

Other exiled archdevils included Bist, Caim, Armaros, Azazel, Cahor, Jaqon, Duskur, Kochbiel, Malarea, Nisroch, and Rumjal, all of whom lived as wandering outcasts in Avernus.

Deceased Archdevils
The consort of Asmodeus and Queen of the Hells, Bensozia was slain by Levistus. The consort of Belial and mother of Fierna. The original Lord of Sixth.
 * Bensozia :
 * Naome :
 * Beherit :