MIA demon lords:
From the 1st edition Monster Manual II, we had a number of undescribed demon lords. All of them were mentioned in FC1 again except for Erishkigel and Nergel. Perhaps they were demon lords and no longer exist; perhaps they were always just gods... wonder if they do have any role in the Abyss anymore at all, or ever did?
Dagon and Nergal were both mentioned in Gygax's and/or Ed Greenwood's Dragon articles on the hells (75, 76, 91), in that both shared named with demon as a form of punishment to them and annoyance for the (more powerful?) demons.
Zanassu was introduced in Empires of the Sands, and reported dead in Demihuman Deities. According to the Empires of the Shining Sea boxed set (1998), page 90, the aranea of Spider Swamp summoned him to fight Qysara Shoon V in 292 DR. Shoon was able to defeat Zanassu and send him back to his Abyssal lair, where Selvatarm eventually hunted him down and defeated him, replacing and impersonating him.
The lord Argolcheir was mentioned in Dragon #116 ("Rogue Stones and Gemjumping") but was said to have been destroyed.
The demon prince Nql was mentioned in the old Eldritch Wizardry book, in the entry on the Codex of the Infinite Planes, and never mentioned again. The question is, just what is Nql? is that the shortened name of another lord? is it an alias of another lord? Is it another non-lord demon? Is it something other than a demon? Is it a legend who may or may not have existed?
Xazivort, a very minor demon lord, appeared in From the Ashes.
Lindyrm was named in the Planescape module, The Deva Spark, but was never detailed beyond a name.
Monte Cook explains Thralhavoc (to the best of his recollection)

"Yeah, that was mine. Honestly, I don't really remember anything about him, or if I even had anything in mind. It was a complete throwaway reference. I'm pretty sure I just needed a cool name. However, I suppose that if, back then, I had been asked to stat him up, I would have continued the Malhavoc theme and made him a demon lord of shadows. Maybe even a bit of a rival of Orcus' hold over the undead (with Thralhavoc being a lord of undead shadows as well). He'd probably human sized, but mostly just a shadow."
Colin McComb responds regarding Zzyczesiya
"I hate to disappoint, but I'm pretty sure that was one of Ray's additions. What you reference was most definitely a throwaway line, but I'll be happy to make something up for you on the spot:
Zzyczesiya, Demon Lord of Confused and Malevolent Ignorance
Abode: A murky land, the features of which defy mapping. Cartographers have noted its tendency to shift the moment they set pen to paper, and while enemies of Zzyczesiya have attempted to overthrow the Demon Thing with armies of map-makers, the result is always tragedy (for the mappers, that is). Lava pools appear, mountains grow where none existed before - or worse, they disappear. The sky of the land is an inky gray, the entirety of which is a portal to neighboring layers (which ones? YOU DECIDE). Creatures fall in and out of it all the time, some on purpose. Most are those who have lost their way through pride or sheer dumb misfortune.
Appearance: Think of a cloak of darkest shifting shadows. Add the fluttering of bats and the incompetent bumbling of moths. Then add an indeterminate numbers of fangs and stingers. Remove a voracious appetite (Zzyczesiya is voracious for nothing, but most especially not for knowledge) but include three wrathful eyes that burn green from everchanging positions inside that penumbra.
Portfolio: Those who resist knowledge in all its forms, those who seek to stamp out learning in an attempt to return to a better time, those who insist on a single worldview and hate dissent - these are all the servants of Zzyczesiya.
Zzyczesiya's powers are amorphous, and the Demon Lord (or is it Lady?) has likely forgotten their full extent, or has otherwise never bothered to learn how far its powers extend. It takes part in the political games of the tanar'ri lords only sparingly, because its rivals outclass it in intelligence and ambition and it resents them for this. Still, each of them seeks to draw Zzyczesiya in to temporary alliances, for the Demon Thing wields incredible brute power. Those who manage to ally themselves with Zzyczesiya are occasionally fortunate enough to achieve their ends - many of them are not, for the Thing directs ill will and ill fortune indiscriminately."
Alzrius had a magic item, the flame amulet of Alzrius, in Polyhedron #135 (written by Erik Mona). Also, while not explicitly stated to be his, one of the armors from the article "Armor of the Abyssal Lords" (Dragon #270) is likely his, as it has a flame theme, and the article says no one knows which lord that armor is attributed to.
Veshvoriak, a deceased obyrith, former ruler of the Iron Wastes. ''Dragon'' #345, "Demonomicon of Iggwilv", page 31.
another demon lord, which someone posted on wikipedia: Gorion - Mentioned in "Dragon Magazine" #139.
Chernovog, who is worshipped by hags and witches in
Expedition to Castle Ravenloft. I don't see a formal declaration of his areas of interest, but his aspect has warlock invocations.
Sha-Hec'urah. The original dungeon geomorph sets (from WAAAAAY back in the day) were broken into three different sets -- low level, caves and caverns, high level dungeons. Each set had a page or so of sample encounters. When the sets were compiled into a single package, only the sample set from the low-level dungeon was included, even though there was some very interesting stuff in the other sets.
Courtesy of Grodog, here's the lost text:
http://www.greyhawkonline.com/grodog/gh_geomorphs.html#geo2
since that fragment is the ONLY reference, I'm inferring he's a prince based on 1. he's named, which means he's at least a "major" demon*, 2. he has a shrine, 3. he has a minor artifact and associated servant, 4. he will appear before you if you aren't careful, and 5. his name is too cool to belong to a non-unique.
* 1e sources varied on the details (and I am w-a-a-y out of practice) but there was a distinction between lesser sorts of demons (types i-iii) who did not have individual names and greater sorts (types iv-vi, princes) which did. Depending on order made a difference in terms of what summoning device you used and (I think) what happens when you kill the demon. I think the lesser sorts were gone-gone, while the greater were just banished to the abyss for a period of time.
Demons and other assorted Abyssal personages:
(mostly taken from
this thread)
Named major demons (form ye olde Monster Manual II index):
Type VI: Alzoll, Balor, Errtu, Ndulu, Ter-Soth, Wendonai
Type V: Aishapra, Kevokulli, Marilith, Rehnaremme
Type IV: Bilwhr, Johud, Nalfeshnee (these were mentioned in the FC1 web enhancement though – nice touch!)
Illssender (Hellbound: The Dark of the War, page 24) A balor, one of the greatest warleaders of his kind, ruler of a tower on the 313th layer of the Abyss (if not the entire layer).
Taramanda (Hellbound: The Dark of the War, page 24) A marilith general, ruler of a sprawling fortress in Blood Tor, catalogued as the 13th layer of the Abyss.
Oulstra (ibid.) A balor, once a nalfeshnee rival of the Marquesse of Loss. Continues to have a bitter rivalry with her former colleague.
Judge Gabberslug (Uncaged: Faces of Sigil) A former nalfeshnee Lord of Woe (like the Marquesse of Loss and Oulstra), exiled to Sigil and the Negative Energy Plane.
Alusiel (Faces of Evil: the Fiends, page 63) A fallen trumpet archon, ruler of the city Mal Arundak in the Rainless Waste (catalogued as the 403rd layer). Alusiel is growing increasingly demonic with the passing years.
Taphaeon (Hellbound [ibid], the Manual of the Planes, Book of Vile Darkness) A nalfeshnee, wielder of the Despoiler of Flesh, ruler of the Fortress of Indifference.
Tarnhem: The balor who formally ruled the layer called Noisome Vale, which is mentioned in the Manual of the Planes and originally appeared in the Dungeon Master's Guidebook by Bruce Cordell.
The Knight Errant: A humanoid demon bound about with rings of cold fire and dripping with lightning. It allows no one who look at it to live, no matter how far it must hunt those who try to flee. From Faces of Evil: The Fiends.
Jaranda (Planes of Chaos, the Book of Chaos, page 24) The marilith ruler of the fortress of Gallowsgate on the Plain of Infinite Portals, she is friendly to the Doomguard.
The Amber Stallion (Ibid, page 32) An armanite, ruler of the largest and successful herd in the layer of Gallenshu.
Vis Nirrin Vis (Ibid) The greatest warleader of the varrangoin.
Keekaku (Ibid, page 33) The nabassu Nursemother, a powerful, enormous, bloated demon dwelling in Pazuzu's realm of Torremor.
Lashan
Ex-ruler of scardale got turned into a lemure/larva.
Lillianth (marilith from the Night Below)
Janelle (alu-fiend from the Night Below)
Villiane (alu-fiend from the Night Below)
Lynnara (succubus from the Night Below)
Ebonbane, a nalfeshnee demon trapped in a sword in the Dungeon adventure "Bane of the Shadowborn." Ravenloft darklord, originates from the Great Kingdom in Greyhawk, apparently
However, according to "Shadowborn", the Ravenloft novel detailing this adventure and surrounding events, Ebonbane is NOT a nalfeshnee, but a unique Abyssal entity. Also Ebonbane's true name is revealed as Lusimar.
Tenser, dretch, from Return of the Eight.
Silussa, the succubus from Queen of the Spiders.
2e Van Richten's Guide to Fiends:
Elsepeth - succubus trapped in Ravenloft
The Whistling Fiend - Babau trapped in Ravenloft
Malocchio - cambion trapped in Ravenloft
The Gentleman Caller - Incubus trapped in Ravenloft
Malistroi - Nalfeshnee trapped in Ravenloft
Baltoi -The Sleeping Beast - Maralith trapped in Ravenloft
- Pallistren (pit fiend; emissary to the aboleth city of Shaboath - from Night Below)
- Shesinellek (marilith; commander in Blood War; sent Lillianth to Prime Material - from Night Below)
- Petrechella (erinyes - from Night Below)
Abaia Bebilith - Abyss The Deva Spark 8
Blarj Bar-lgura - Abyss The Deva Spark 14
Chiryn Succubus - Abyss Well of Worlds (3) 45
Henjar Balor - Abyss Well of Worlds (4) 52
Meerena Succubus - Abyss The Deva Spark 14
Miirta Balor - Abyss Well of Worlds (4) 52
Norglemist Nabassu - Abyss Chaos - The Book 19
Riza Marilith - Abyss Well of Worlds (4) 52
Za'rafas Tanar'ri (KIA) - Abyss Manifesto 123
Hissboda Tanar'ri - Abyss (Naratyr) Chaos - Travelogue 14
G'oud'neejh Glabrezu - Abyss (Plain of Infinite Portals) In the Abyss 18
Haarsa Alu-fiend - Abyss/Plague-Mort Well of Worlds (7) 97
Latana Succubus - Abyss/Plague-Mort Well of Worlds (7) 97
Marquis Fearson Marquis Cambion - Abyss/Plague-Mort Well of Worlds (7) 95
Mortai Major Cambion - Abyss/Plague-Mort Well of Worlds (7) 95
Stkal Bar-lgura - Abyss/Plague-Mort Well of Worlds (7) 97
Fosnatu'u Tanar'ri - Rigus Manifesto 18
Ugrek Hezrou - Sigil (Lady's Ward, Temple Abyss) In the Cage 44
Marisha the Fox Alu-fiend - Sigil (Lower Ward) In the Cage 50
Tattershade, King of Rats Shadow Fiend - Sigil (Lower Ward) In the Cage 50
Rantash Quasit - Xaos Source Box - Sigil 50
Dungeon 10 : Athoz (alu-demon)
Nangir (cambion)
Tuerny the Merciless (of the Iron Flask of Tuerny the Merciless) appeared in he adventure Return of the Eight as a stronger-than-average nalfeshnee.
Sinmaker - Glabrezu poisoner in MotP
War of the Spider Queen Book VI: Resurrection
Zerevimeel: Nalfeshnee
Vakuul: Chasme
Jot, Quasit - Sunless Citadel (a run of the mill quasit, I believe)
Idalla, Succubus - Forge of Fury (a run of the mill succubus, I believe)
The Cuckoo, Vrock Bard - Standing Stone (presumably referenced again in Heart of Nightfang Spire)
Rhunad, Vrock - Heart of Nightfang Spire (a run of the mill vrock)
Ammet, Half-Dragon Balor - Bastion of Broken Souls (the original was advanced to 19 HD. It is unclear if it should be advanced in 3.5 rules, but presumably not; was bound as Ashardalon's heart; Has a three-strand artifact whip named Helltongue; called Eater of Souls)
(Ashardalon, Half-Fiend Great Red Wyrm - Bastion of Broken Souls; bound Ammet as his heart)
The Cathezar, Half-Chain Devil/Half-Marilith - Bastion of Broken Souls (originally a servant of Demogorgon/Aameul; depending on events, she may be either dead or serve Ammet now)
Buphalthus, Balor - Bastion of Broken Souls (has 2/day Implosion SLA instead of fire storm)
Tamion, Balor - Bastion of Broken Souls (Wields a +3 vorpal unholy greatsword; also has a cloak of resistance +4 and a belt of giant strength +6)
Alzoll ... Alzoll has not yet appeared in the Realms, IIRC.
Errtu ... Errtu first appears in "The Crystal Shard", reappears in a later novel, possibly "Passage to Dawn".
Ndulu ... Ndulu first appears in Dragon #91, a write-up that is reprinted in FR4 - The Magister. He is mentioned in Sea of Fallen Stars and flushed out more (including parenthetical stats) in Champions of Ruin under write-up of Eltab.
Ter-soth ...Ter-Soth first appears in H4 - The Throne of Bloodstone, page 47
Wendonai ... Wendonai is detailed in Lost Empires of Faerun, pages 52, 54-55.
Grintharke -- appears in I12- Egg of the Phoenix and brought into the Realms in FR5 - The Savage Frontier. Killed off in Hellgate Keep and The North backstory.
Book of Vile Darkness - Ykkandri, possessor glabrezu ('currently' possessing Enesstrere, ancient blue dragon)
Jaziritheil (wastrilith - from Night Below)
Blackhelm was a babau demon with a cursed helmet on (from which he took his name) in Reverse Dungeon (2E). He had recently escaped from the Demiplane of Worms.
FR4 The Magister: page 57, the sword Demonbane was used to cause Ndulu to flee from the Material plane.
FR5 The Savage Frontier page 8, 42, 59, and 63; Grintharke the balor was the ruler of Hellgate Keep (at the time FR5 was written).
page 54, according to legend, the hero Beorunna destroyed the nalfeshnee Zukothoth by collapsing a cavern on both of them.
FR7 Hall of Heroes page 18 and 78 features The Earth Spider, listed as a powerful demon.
Hall of Heroes also mentions Phalse, a humanoid demon with the head of a beholder who disguises himself as a halfling.
Phalse also appears as an ally of Moander and others in the novel Azure Bonds, if I recall correctly.
MacDaer (major cambion, Dungeon #13)
War of the Spider Queen series
Aliisza: female Alu-demon
Jeggred: male Draegloth
Kaanyr Vhok: male Cambion
War of the Spider Queen Book V: Annihilation
Raashub: male Uridezu
Belshazu: male Glabrezu
The Fiend-Sage of Rel Astra originally appeared in Ivid the Undying. The Fiend-Sage is the molydeus advisor to Drax, ruler of Rel Astra in the World of Greyhawk. It is known for dressing in mortal finery, and it is a brilliant scholar.
Dragon Claw (whose real name is, IIRC, Lung Jua) was described as a demon lord, although not a tanar'ri, in the 2E FR adventure Mad Monkey vs Dragon Claw.
Tarnhem, a balor, is in Return to the Tomb of Horrors. I don't think any of the other tanar'ri there are named, however. Tarnhem is the father of Acererak, and his layer of the Abyss is covered in the 3E Manual of the Planes.
Fall-From-Grace, a redeemed succubus (IIRC she's CN), is from the Planescape: Torment computer game. She also appears in the Torment novel, and has her stats given in Dragon #264.
Also, A balor named Raachaak, and three vrocks named Shaakat, Rejik, and Morbaat appear in The Paladins, by James M. Ward and Davis Wise, book two of the Forgotten Realms's infamous Double Diamond Triangle Saga. The three vrocks are all dead by the end of the book, but I don't recall offhand whether or not Raachaak appears in the later novels, or what happens to him.
Dragon #24, the "Ramifications of Alignment" article, the last god mentioned is Thakta Tylden, a chaos god of war. It mentions that he oftentimes sends one or more of his sons to fight for him, unless a battle is apocalyptic. One of the listed sons is Dakunth, a 20th-level Type VI demon.
Byakala is an advanced marilith with the Smoking Eye template, found in The Shackled City.
From the Book of Vile Darkness web enhancement, Rhyxali has two demon servants, a marilith sorcerer named Viractuth, and an advanced elite shadow demon named Kadasha.
There are two cambions laid down in Iuz the Evil: Baron Kerzinen of Rookroost, and Marionnen.
The last Spelljammer novel, The Ultimate Helm, by Russ T. Howard, had (what appeared to be, from the description) a glabrezu named Lord Mowg.
babau known as Kaxathros from the Dungeon adventure "Prism Keep". (Dungeon #45, pg. 61-62). INT genius; HD 8+14; +7 STR bonus; bardiche +1.
in the adventure "Bzallin's Blacksphere", in Dungeon #64, aside from the demon lord Jzzalshrak, the following named demons appear:
Koroxon, babau
Yazbat, quasit
Gloomwhisper, shadow demon
In Dungeon Issue #70, the adventure called Kingdom of Ghouls (pg. 62) gives stats for a glabrezu named "Crumhorn".
Kizarvadexus is a demon of unspecified type slain by the Wind Duke Zosiel. (Dungeon #129)
More info can probably be found here:
http://d20npcs.wikicities.com/wiki/D&D_Named_Demon_Project