Demon lord

Demon lords, also known as Abyssal lords, are demons who have gained great power and established a position of preeminence among demonkind. Each demon lord has a unique appearance and set of abilities. Most control at least one layer of the Abyss. A demon lord, when slain in a plane other than the Abyss, is banished to the Abyss for a hundred years, whereas ordinary demons, including the mightiest balors and mariliths, risk being reborn into a lesser form, or not all. The most powerful demon lords are demon princes. Demon lord and demon prince are self-proclaimed titles; unlike the archdevils, the chaotic evil demon lords do not have a rigid hierarchy.

Demon lords wage eternal war with each other, often seeking ways to expand their holdings into other layers and at the same time defend their personal domains from rival lords and scheming underlings. Demogorgon has for many years been the most powerful demon lord, and he proclaims himself Prince of Demons. Orcus and Graz'zt contest his title.

Most demon lords have secretive mortal cults who seek to elevate their lords to godhood through prayer and sacrifice. Book of Vile Darkness details a number of prestige classes for mortal disciples of demon lords, as does the "Demonomicon of Iggwilv" feature currently running in Dragon magazine.

Almost all demon lords control a layer of the Abyss, and many have a scattering of mortal worshippers, whereas all demon princes control at least one layer of the Abyss, and all have mortal worshippers.

Known demon lords
The most common known demon lords are Baphomet, Dagon, Demogorgon, Fraz-Urb'luu, Graz'zt, Juiblex, Kostchtchie, Lolth, Malcanthet, Obox-ob, Orcus, Pale Night, Pazuzu, Sess'innek and Yeenoghu. The majority of these below demon lords appear as listed in Appendix I in Fiendish Codex I: Hordes of the Abyss. (o) indicates an obyrith, (l) indicates a loumara, and (d) indicates a lord that is presumed dead. Note that any demon lord who was mentioned by name only in the Monster Manual II (1983), on page 35, is noted as "*MM2".

Non-canonical demon lords
Green Ronin published a D&D d20 supplement entitled Armies of the Abyss (2002, reprinted in 2003 as part of the Book of Fiends compilation) that provides information on 21 demon lords. The similarity in names between Green Ronin and D&D demon lords is coincidental: like many D&D demon lords, Green Ronin demon lords draw their names from real world mythology. Demon lords that share their names with D&D demon lords are listed in bold.

A number of minor lords were also detailed in Armies of the Abyss:
 * Cresil the Impure (may or may not be equated with Gresil).
 * Eurynomous the Corpse Eater
 * Malohin the Strangler
 * Merihim
 * Philotanus the Seducer
 * Rahu the Tormentor
 * Shiggarebb, Lady of the Qlippoths

Gary Gygax, in his Gord novels: "The Sea of Death", "Come Endless Darkness" and "Dance of Demons", mentioned many other demon lords. These include:

Necromancer Games, in their Tome of Horrors I and II listed alternate statistics of official demon lords Baphomet, Dagon, Fraz-Urb'luu, The Faceless Lord (aka Juiblex), Kostchtchie, Orcus, and Pazuzu. They also include:
 * Beluiri, a demoness consort of Baphomet.
 * Maphistal (not to be confused with Mastiphal), a lieutenant of Orcus.
 * Sonechard, a general of Orcus.
 * Tsathogga, the "Demon Frog God".
 * Caizel the Seductress.
 * Vepar, a vassal of Dagon.

Mongoose Publishing's "The Slayer's Guide to Demons" include the following:
 * Iyaviht the Dark Whisper, Patroness of the Jartaska.
 * The Gatekeeper, an exiled prince on the first layer of the Abyss

The book also introduced several so-called "Nameless Ones", ancient and powerful demon lords said to be the first demons:
 * The Dancer in Darkness
 * He Who Dreams
 * The Demon Mother
 * The Foundation
 * The Silence at the end of Eternity