As the Demon Princes are to Tanar'ri and other demons, so too are Archdevils to Baatezu and other devils. These are the demigod-like rulers of the Nine Hells of Baator, or just plain Hell if you're coming from Pathfinder, the commanders of the diabolic legions and the other major contestants for Big Bad Evil Guys for players to defeat.
Because D&D's devils have a certain Abrahamic influence, there are traditionally far fewer of them than there are Demon Princes; in fact, in some sourcebooks, the Archdevils are the same thing as the Archdukes, which means that if you don't count their boss Asmodeus as one of them, there's only ever eight Arch-Devils in total, plus a handful of former Archdukes who have the power but no longer have the authority. Who's who depends on which edition you're looking at. Other editions make it clear that there Archdevils consist of both Archdukes - the layer rulers - and Dukes, which are Archdevils not quite strong enough to have their own layer.
Pathfinder, in comparison, has a much fuller roster of Archdevils; as well as Infernal Dukes like in D&D, there are also the Malebranche - unique and powerful devils strong enough to ravage worlds themselves, essentially a next tier down from the Infernal Dukes, and the Whore Queens - a band of four female fallen angel archdevils who have risen as high as they can in the misogynistic hierarchy of Hell, and whose cults are comparable to those of the Archdukes.
The Archdukes of Baator
- Level 1, Avernus: Bel or Zariel or Tiamat
- Level 2, Dis: Dispater
- Level 3, Minauros: Mammon
- Level 4, Phlegethos: Belial and Fierna
- Level 5, Stygia: Levistus or Geryon
- Level 6, Malbolge: Moloch then Malagard then Glasya
- Level 7, Maladomini: Baalzebul
- Level 8, Cania: Mephistopheles
- Level 9, Nessus: Asmodeus
- Level ???: Gargauth
In contrast to the above, these Archdevils never were rulers of the nine layers of Baator, but they're still powerful figures in their own right.
A powerful vassal of Mammon, who is also known as the Bronze General. Whilst he's a brilliant tactician, politically, he's kind of inept. Nothing pisses him off more than to have his legitimate accomplishments rendered null or stolen by some slimy weakling whose only talent is scheming, so he'll often hire outside adventurers to help compensate for his lack of political acumen.
An ascended pit fiend servant of Mephistopheles renowned for both his loyalty to his master (which makes other devils think Mephistopheles has some big-league blackmail on him) and his hatred for mortals. Unlike most devils, summoning Hutijin just results in a torturous death as he takes out his rage about being taken from Cania on his unlucky summoner. Because of this, other archdevils have taken to liberally handing out Hutijin's personal phone number, resulting in his days often being interrupted with annoying calls he has to take because they yank him to another plane. His rivals do this because first of all, it's hilarious, and secondly, all time Hutijin spends on the Prime Material torturing some hapless berk who called the wrong hell-number is time that Mephistopheles spends without his greatest servant, potentially leaving him vulnerable.
Even the most paranoid of individuals are prone to listening to what they wish to hear; so long as what you're telling them is 'you have enemies everywhere', they might even accept the implicit premise of 'I'm not one of them'. No one knows this better than Titivilus, seneschal to Dispater. While Dispater, unlike many paranoids, really does have people plotting to attack or betray him, Titivilus has stoked his paranoia beyond what is reasonable even by devilish standards, encouraging Dispater to seclude himself completely and leave most of the day-to-day rulership of Dis to Titivilus- a task he's succeeded at so well, some people think he actually is Dispater.
But despite how well his plan has been going, Titivilus is aware that he rests in a very precarious position. All it would take is one slip-up, one inconvenient surprise, or one devil snitching on him for Dispater to notice his schemes and probably either kill him or torture him for eternity. So Titivilus spends a lot of time trying to smooth over rough edges and snip loose threads in his carefully-constructed deception, and often hires adventurers to help him with this, usually either killing some problematic devil or doing the grunt work in getting another of his plans into action.
In Pathfinder, these are the reigning archdevils of Hell.
- Layer 1, Avernus: Barbatos
- Layer 2, Dis: Dispater
- Layer 3, Erebus: Mammon
- Layer 4, Phlegethon: Belial
- Layer 5, Stygia: Geryon
- Layer 6, Malebolge: Moloch
- Layer 7, Cocytus: Baalzebul
- Layer 8, Caina: Mephistopheles
- Layer 9, Nessus: Asmodeus
|The Fiends of Pathfinder|
|Lawful:||Asuras - Devils - Rakshasas - Velstracs|
|Neutral:||Daemons - Divs - Sahkils|
|Chaotic:||Demodands - Demons - Qlippoth|
|Lords:||Ahriman - Archdevils |
Demon Lords - Four Horsemen
|The inhabitants of the Planes of Planescape|
|Upper Planes:||Aasimon - Angel - Animal Lord - Archon |
Asura - Eladrin - Guardinals - Lillend
|Middle Planes:||Formians - Githzerai - Inevitable - Marut |
Modron - Rilmani - Slaadi - Kamerel
|Lower Planes:||Alu-Fiend - Baatezu - Bladeling - Cambion |
Demodand - Erinyes - Hag - Hordling
Imp - Kyton - Loumara - Marilith - Obyrith
Succubus - Tanar'ri - Yugoloth
|Transitive Planes:||Astral Dreadnought - Githyanki|
|Inner Planes:||Azer - Elemental - Genie - Grue - Mephit |
Salamander - Sylph
|Sigil:||Dabus - Cranium Rat|
|High-ups:||Archangel - Archdevil - Archfey |
Archomental - Demon Prince