Demon lord

Demon lords, also known as Abyssal lords, were archfiends who gained great power and established a position of preeminence among demonkind. Each demon lord had a unique appearance and set of abilities. Most controlled at least one layer of the Abyss. A demon lord, when slain in a plane other than the Abyss, was banished to the Abyss for a hundred years, whereas ordinary demons, including the mariliths and glabrezus, risked being reborn into a lesser form, or not all. A demon lord who had complete control over an entire layer of the abyss was known as a demon prince. Demon lord and demon prince were self-proclaimed titles; unlike the archdevils, the chaotic evil demon lords did not have a rigid hierarchy.

Demon lords waged 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 had, for many years, been the most powerful demon lord, and proclaimed himself Prince of Demons - a coveted status symbol since the Age before Ages. Orcus and Graz'zt contested this title.

Most demon lords had secretive mortal cults who sought to elevate their lords to godhood through prayer and sacrifice.

Known demon lords
The most commonly known demon lords were 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