: Directly controls only a very small territory, dead center in the middle* of the infernal realms. His stronghold perches on the edge of the abyss, with one twelve mile long bridge extending to a secondary fortress on the far side, and catacombs extending downwards for at least an equal distance. It is said that the lowest reaches of his domain look out on where the titans themselves lie sealed away, and that this is why he pays so little attention to the mortal world: nearly all of his focus goes towards finding a way to free his masters.
* Given that the geography of the realms is neither constant nor euclidean, this is more a matter of defining the middle to be where Nathrezell is, than any actual statement about the location of his domain.
Mortal view: Who?
, the Lord of Darkness: Terobog is dead, and all agree that this is a good thing. He was defeated by the Sun Lion at the end of the third age, and lay dying in his keep for centuries until Nathrezell broke the last of his defenses and finished him off. See also Ishruk, Kerberos, and Lillith.
Mortal view: A demon lord, you say? Never heard of him.
: The first demon lord that Nathrezell crafted from the remains of Terobog. Declared a failure and cast aside. (Though some claim it broke free under its own power.) It now lurks in the deepest depths of the abyss, devouring all that cross its path. It is also an interesting anomaly that Nathrezell allowed a failed experiment to continue to exist; generally a being involving that much expenditure of raw materials would be simply broken down and reforged until the original goal was achieved. This is usually viewed as evidence in support of the "it broke free" theory, as tracking down and re-capturing a major demon lord could easily be more trouble than it's worth.
Ishruk is both formless and mindless, similar to an ooze or chaos beast or gibbering mouther. Its surface is broken by countless mouths and claws and eyes, and dotted with patches of gray-green scales.
Mortal view: Ishruk is the ultimate terror of the lightless places far beneath the earth, and appears in both dwarven and kobold lore - most often as the patron of a cult of destruction, or as a being that fosters madness among those caught in cave-ins. Still, references to Ishruk are not common, and - especially outside those two races - only those with some religious training are likely to recognize the name.
: Controls all but one tiny corner of the lethean ocean, and most of the lakes and rivers of the infernal realms. Holothurion is probably second in power after Nathrezell, but the aquatic nature of her minions makes it difficult for her to expand her reach. She is at war with every demon lord that borders the lethean ocean itself, but has numerous allies outside that region.
Holothurion's natural form is a monstrous sea snail, and her venom is legendary for both its potency and its varied effects; she is said to be able to slay (or paralyze, or otherwise critically inconvenience) even creatures that should be immune to poison with but a single sting. When not using her natural form, she typically appears as a sahuagin.
Mortal view: Holothurion is the lord of the deeps, a monster so great that hunting even kraken would be beneath her notice. Mentioning her name while within sight of the ocean is said to be bad luck, and doing so within earshot of a sailor is an easy way to ensure that you cannot find a crew willing to let you step on board. Almost any evil upon the ocean waves will have her mark upon it, and the most bloodthirsty of pirates are those who seek to earn her favor.
: Controls one tiny corner of the lethean ocean, and the fens and waterways around that region. His primary trait is tenacity; despite being one of the lesser demon lords, he and his forces have held out against Holothurion's fury for centuries – though a careful student of history may note that he is slowly losing ground. Of course, part of his success is due to support from other demon lords around the lethean ocean, who realize that when Naknak falls, Holothurion will have far more attention and power to spare on fighting them.
Naknak is a bizarre semi-humanoid frog-demon, with enormous bulbous eyes, a hunched-over form, and numerous multi-colored fins and frills. Don't laugh at him. He hates that.
Mortal view: A few shoreline tribes pay fearful tribute to Naknak, and some rare dark shamans seek to spread his power farther afield. Still, most mortals are blissfully unaware of him.
: Ingram is dead, slain by Terobog sometime during the third age, but his spirit was trapped in five talismans. Three of those are held by his lieutenants, Adrak, Kadra, and Nameless, and their power is sufficient to hold Ingram's current territory. One of them was kept by Terobog, and its whereabouts (or even continued existence) are unknown. The fifth is held by Ingram's sworn enemy, Skevryn. As it is, Ingram is one of the competitors for second strongest demon lord; were he to recover the remainder of his soul and resurrect himself, he might come close to competing with even Nathrezell.
Ingram was a burrowing serpentine demon, somewhat similar to a purple worm. Occasionally he temporarily grants that form to one of his lieutenants (usually Nameless), but most beings of this age simply consider Ingram to be an incorporeal force, or an invented 'superior' to justify a long-lasting alliance of lesser demons.
Mortal view: If you find a cult of plain old generic demon-worshippers, it is most likely that they follow Ingram - whether they know it or not. Ingram is fond of all the old-fashioned techniques: evil viziers and chancellors, vicious and militaristic rebels, kidnappings and sacrifices, and implicating those who would have most strongly opposed his efforts and letting mob "justice" do the rest.
: Along with Ingram, Scrygnimir, and Agrinistryx, she was one of Terobog's lieutenants during the third age. She was also one of Terobog's favorite toys, and would love nothing more than to get her claws on one of the remaining pieces of the lord of darkness and return the 'favor'. Well, ok, maybe one thing more: dominion over the infernal realms. Starting with Ingram's territory.
Her form is classic demon - mirror-bright red scales over a perfect human body, framed by cloven hooves, claws, fangs, swept back horns, a long lashing tail, and fire where she ought to have hair, all scaled up to a height of about twelve feet. Her greatest personal power is regeneration; injuries that would be instantly lethal to lesser beings heal in mere seconds, though it is said that even she took weeks to recover when Terobog turned his attentions to her.
Mortal view: The patron of succubi and incubi. While nearly all demon lords take some advantage of carnal temptations, Skevryn is particularly well known for this tactic - a reputation that she takes ruthless advantage of, sacrificing comparatively obvious pawns to hide more subtle manipulations.
: Terobog's old fortress sits across the only usable pass in the titanspine mountains - which sit between the territories claimed by Ingram and Skevryn. After Nathrezell cleared out the last of Terobog's minions, he granted both the citadel and Kerberos to Gjear, in exchange for some unknown favor. Though she was sandwiched between two of the greatest powers of the infernal realms, Gjear held her fortress for over two thousand years; the presence of two demon lords, along with remnants of Terobog's defenses, rendered her domain too expensive to conquer. (Either of her neighbors *could*, of course, but doing so would deplete far too many resources and leave them vulnerable to attacks from elsewhere.)
Recently, Kerberos vanished from the citadel - replaced by a massive influx of lesser demons. For a few weeks, Gjear was able to actually push out from the walls of her citadel, claiming and holding territory that had long belonged to Ingram. Then whatever new power she had found gave out. Her citadel is now a continual pitched battle between the forces of Ingram and Skevryn, and the defenses of the ancient fortress, now turned against themselves, threaten to tear the very mountains asunder.
Skevryn claims to have captured Gjear, but nobody seems to know if that's true or not.
Gjear is a cat-headed flying serpent, with powers tied to wind, acid, and illusion.
Mortal view: Gjear is not so well known, in part because her plots and orders for her mortal servants tend to be fairly straightforward and predictable. She has a tendency to forget that even illusions can be seen through, and that experienced adventurers won't always trust initial appearances.
Kerberos, the Broken
: The second of Nathrezell's experiments with the remains of Terobog. Also considered a failure, though less of one than Ishruk was.
Mortal view: Only fairly studious religious scholars are likely to recognize Kerberos' name.
Kardom, Kria, & Kalthalak
(also known as The Three): This three-headed dragon was one of Nathrezell's lieutenants during the third age, and though he seems to act independently now, it is widely believed that this is merely because Nathrezell has not bothered to give him any orders within the past millennium. His domain is a series of floating islands, drifting far above the typically earthbound territories of most other demon lords.
Kardom is a blue dragon and a vicious melee combatant - he usually controls the combined body.
Kria is a yellow dragon and a powerful sorcerer - though she often complains about being stuck in a definitely male body, and frequently makes use of spells that let her manifest her own separate form.
Kalthalak is a green dragon. He usually doesn't say much, seeming content to let the other two do what they will.
Mortal view: The Three sponsor a wide variety of dragon cults, and are responsible for most of the corrupted dragons in the world. They also quietly sponsor dragon hunting parties - though any such party that discovers the true nature of their sponsor would do well to seek other pasttimes before they meet death at the claws of some chosen champion of the Three.
: The only white dragon known to combine great age with a still fully intact form*; as a demon lord, her direct connection to the Titans grants her the energies needed to avoid the otherwise inevitable decay. She does not, however, extend this courtesy to the undead under her control; her descendants from when she was alive now serve her in various states of death and decay. (Persistent rumors claim that some of her brood yet lives, albeit many generations removed.)
Condensing Fel Ice's name to one word is generally fatal - either from indignant fury or from being cuddled like a teddy bear by a being whose very presence leeches both heat and life.
Mortal view: Fel Ice is the (current) demon lord patron of undead, and often closely associated with Atrus, or (wrongly) stated to be subordinate to Atrus - the average person doesn't really care about the distinction between a demon lord and a vile god.
* Scrygnimir and Agrinistryx also managed this, supported by a combination of Terobog's energies and daily sacrifices. And they were far older than Fel Ice, who only dates back to the middle of the third age. Of course, they were also destroyed during Terobog's battle with the Sun Lion.
: An anomaly among demon lords, Hecate has few minions and no territory within the infernal realms. The majority of her followers are mortal disciples dedicated to the advancement of magical knowledge at any cost.
Legend states that Hecate mastered both divine and arcane magics, and, having learned all that could be learned from those paths, turned her back on her gods and began delving into the secrets of the titans.
Do not take this to mean that she is any less dangerous than other demon lords, though - she has a vicious temper, and a truly remarkable arsenal of deadly spells that really do need just a bit more testing and fine-tuning...
Her typical form is draconic; largely green, but set with poisoned purple spines and golden runes. However, she also uses a wide variety of humanoid forms, and seems to have found some method of confounding even the most powerful of detection spells - so her actual true form is unknown.
Mortal view: The order of paladins estimates that as many as one fifth of Hecate's disciples are not caught during their lifetime - and this is almost certainly an underestimate; Hecate does not tolerate those foolish or reckless enough to make a mess in their own back yard. Indeed, living near a disciple of Hecate is often good for the locals - they get an at least reasonably competent spellcaster with a strong vested interest in making sure that adventurers (and especially paladins) have no reason to investigate their home turf.
: The third of Nathrezell's experiments with the remains of Terobog. Little is known of her or her fate; she does not reside in the infernal planes anymore, if she still exists at all. Rumors vary from saying she was also deemed a failure and destroyed or cast out to the material plane, to saying that she managed to ascend to the status of a minor vile god.
Lillith is (or perhaps was) a naga, with the ability to assume both a fully serpentine or fully humanoid form. She favors (favored?) fire, darkness, and domination magics.
Mortal view: Much like Kerberos, most mortals haven't heard of Lillith.
: The first Barghest. Created as an experimental new type of harvester demon; smaller and more able to evade detection by powerful adventurers than a typical mobile fortress design. Vulf proved far more competent than his creator had intended, and, upon his return from his first test run on the material plane, devoured his prior master and took up the mantle of the Worg Lord. Several other demon lords have attempted to create similar designs, with little success. Even Vulf himself has been unable to create more barghests by any means other than breeding with worgs - and the resulting watered-down creatures are much lesser beings than Vulf himself.
Mortal view: Vulf is a well known terror of any frontier area - or anywhere else with enough room for a pack of wolves nearby*. Cursed werewolf outbreaks, and any form of wolf-cult are typically blamed on him, regardless of his actual involvement in the matter. City dwellers, by contrast, typically regard stories of barghests as more of a joke than a serious threat.
* Actual wolves hate Vulf and his minions just as much as most humans do. Unfortunately, few humans really care to make the distinction.
the Pure: Was once a paladin, so certain of his faith and righteousness and power that he raised an army to assault the very gates of hell. For a time, his crusade went well, and two demon lords perished by his blade. But the dangers of the infernal realms are not purely physical in nature, and with each victory, Alamar's hubris and mad certainty grew - now he seeks to release the Titans, that he might challenge them to single combat and rid the world of their evil once and for all. Any sacrifice is worthy in the name of that final goal - and if he must send his minions back to the material plane to harvest the souls of the innocent, so be it.
Mortal view: Alamar's name is a curse. His followers have been responsible for some of the most repressive and bloody regimes in recent history; kingdoms where even the slightest immorality was outlawed, and even the lightest of crimes held the death penalty. And death, of course, meant a ritual sacrifice to Alamar himself, offering up the soul of the departed to be cleansed by fire and purged of evil. Let the other demon lords have their corrupt advisors and ladies of negotiable virtue; Alamar will take the lowly watchmen and minor magistrates and executioners and grant them the gift of unswerving faith and righteousness.
: Originally a water elemental lord in service to Holothurion, Thasselion attempted to follow Naknak's example of rebellion. However, he made the mistake of opposing her directly, and Holothurion's sting poisoned him with elemental ice. His frozen form has been significantly reworked since then, with tunnels and chambers cut deep into his body, and his loyalty to Holothurion enforced by runes carved into his very heart. Now, he serves Holothurion as a floating fortress; a home for those few of her minions who cannot live beneath the ocean's surface. While his physical abilities are no longer relevant, Thasselion remains capable of potent magical attacks, especially against those who dare to enter his interior.
Mortal view: Thasselion is largely unknown; he has few followers of his own, and can only influence the mortal world when Holothurion allows him to do so - which, given his past treachery, is rare.
: A massive flying fortress. Originally a non-intelligent construct built by Terobog to counter the threat posed by the Three. During Terobog's defeat, it was damaged and crashed into a field of felvine*. Between the fort's imperative to repair itself, and the felvine's ability to adapt and proliferate, it did not take long for the combined being to return to the air. Though it is now at least somewhat sentient, Jadethorn's goals are fairly simple: Destroy the Three. Exist. Spread its seeds as far and wide as possible. This third goal is the most dangerous; its felvine components have adapted to living with an existing host, and thorn zombies now serve the fortress in the much the same way that living demons once provided it with crew and shock troops.
Jadethorn despises dragons of any sort - though it will admit that, properly zombified, they do make excellent fertilizer.
Mortal view: Jadethorn is relatively poorly known, its following limited to the occasional mad botanist or druid - and, of course, plant creatures of all sorts.
*Felvine is like kudzu. Except it grows much faster, is carnivorous, and has poisonous thorns capable of ripping through most forms of light armor. As an added bonus, the stuff is also highly resistant to hostile magic. It does make a wonderful material for constructing ropes and (coarse) cloths, though - assuming you can convince it to stay dead.