The underdark is a dangerous subterranean network of tunnels and caverns stretching out beneath Faerun's surface. Generally only expored by the most well prepared of adventurers, it is a highly hostile enviroment that anyone would be well advised to simply avoid if at all possible.
A network of tunnels, the Underdark is almost completely devoid of light, and is home to some of the most fearsome creatures that Faerun has to offer, including hook horrors, creatures with natural plated armor and incredible hearing that use sound to see, much like bats. Dragons, generally of the less... nice variety. And often thought as the most dangerous of all, the Drow, dark elves that delight in cruelty chaos and deceit. Living in the Underdark is often a day by day affair, with each day bringing untold dangers and possible death. Even if you find yourself within the relative safety of a city, such as one of the deep gnomes cities, disaster is quite possible, or even likely.
Adventuring here is strictly for the strong-hearted and well-prepared. This subterranean environment often completely lacks sources of light, food or water, and underground volcanic activity can poison the very air (or lack thereof) that a traveller breathes. Finding civilisation is hardly any comfort; a number of strange races are present to accost a traveller -- though thanks to Luxord's intervention one danger has been eliminated in the form of the illithids.
Alan Schezar's men found a portal to the Underdark and helped one of the Drow Kingdoms fight off an assault of Shadow Dragon-Drow half-breeds, and the matriarch sent them off to take the fight back to the half-breeds. Upon capturing one of the commanders and making their way back, the pirates sealed an alliance between the kingdom and the Phoenixes of Armageddon.
Multiverse-based adventurers have only been able to discover two major Drow settlements: the cities of Erelhei-Cinlu and Guallidurth. These are both Middledark cities.
- Pholzubbalt (aka: The Boneyard, The Mausoleum City): An ancient city, with a population of well over 5,000 inhabitants. Only 5 are living, and two of them are aspiring to lichdom. Most of the rest are mindless undead, such as skeletons and zombies, though wraiths, shadows, ghouls and ghasts are also common. It was forgotten until, half a century ago, a lich named Ulpharz discovered it, and was delighted by a city of coffins and necromanic rituals and secrets. It was found by adventurers who hastily retreated, christening it The Boneyard, and marking it as a place to avoid.
- Drow: The Drow are a matriarchy, and almost all noble female drow are Priestesses of Lolth. Each city is usually overseen by a council of the ruling Matron from each of the agreed on ten most powerful houses. Each Drow city will have a main temple to train new priestesses, a school of arcane magic for select drow males, and a school of combat for the rest of the noblemen. Each House has it's own compound, with elaborate security, and their own shrine to Lolth, to pray, usually not for help, but rather to be tested that they may prove their strength and cunning.
Physically, Drow skin ranges from "dark grey, to polished obsidian" (Source book's phrase). Their hair is usually white or silver, but occasionally very pale yellow is seen. Their eyes can be almost any color, including blood red. (That's right, red isn't the most default) Drow are slightly shorter and more slender than humans, but they are surprisingly strong for their size. The vast majority of Drow could be termed "above average" in terms of attractiveness, due to the selective nature of the race and their goddess, with any child born with a deformity killed immediately. In combat, they prefer poisons and crossbows, favoring stealth over open attacks. This is not to say that open attacks do not occur, but they are far less likely to succeed.
Drow speak Undercommon, and a dialect of Elvish that is different, but understandable. Their unique form of communication is the hand signs they've developed, which can stand in for actual speech with little difficulty, and nearly all Drow understand fluently.
- Chitine: These beings were once more humanoid, but the Drow found them, and through twisted magical experiments turned them into what they are today. The average Chitine stands at just under 4ft. tall, and weighs around 85lbs. They have four arms, each with two joints, instead of the usual one. The face is humanoid, but with multifacted eyes, like those of a fly, and small mandibles just from the bottom of their mouths. Their skin is mottled grey, and their hair is a tangled black mess, that goes down their back like a horse's mane. An aperture on the front of their abdomens allow them to spin with their own webbing, and they can create even weapons and armor given time. They secrete an oil that prevents them from getting stuck on any form of webbing, and their hands and feet have tiny hooks, too small to be seen, that allow them to climb walls and ceilings.
- Deep Imaskari: Deep Imaskari appear generally human, but their skin is pale and stone-like, appearing to be carved from fine marble, though it is as soft as a normal human's skin. They are tall and slender, the men stand at 5 and 3/4 to 6 feet tall and weigh 160lbs, and women are about a half foot shorter and more like 120lbs. Their fashion preference is for elaborate greatcoats, over elegant black shirt, with matching trousers and boots. They have a particular love of dark rings, doubly so when magic is involved.
The Deep Imaskari are intelligent, but physically slightly clumsy and off-balance. They don't fall down stairs, or such, but they are on the whole less graceful or at home in their bodies than many other races. They can see twice as far as a human in poor lighting. When underground, they are hard to spot. Their marble skin naturally blends into the background of the Underdark.
- Duergar: Short, ash-skinned, white-eyed beings about half the size of a human. Or shorter. They are evil, but mildly less so than the Drow. They are self-centered and concerned with wealth, and fending off their main enemy, the Drow.
- Illithids: The psychic race of squid-headed monsters, this race was thought to be obliterated, however it turns out that all that was accomplished was the destruction of a single group of them, with many others living in other areas of the underdark, it is unlikely that anything lasting or even significant was accomplished.
Pretty much everything right above here can be attacked and are just as likely to attack you. Besides them, however, are a number of beasts of varies types.
Umberhulk: Giant brutish monsters that act more like tanks than real monsters. They can take huge amounts of damage and are used by both Drow and Illithid forces as living battering rams. Worse still, they can confuse their enemies and cause them to become disoriented and lost.
Earth Nodes: Pockets of elemental energy, that people with enough training can tap to gain spells, store items, and empower their magic, though any spellcaster can do the last. Half of all nodes are weak, usually only about 30ft in diameter. A quarter are one degree stronger, with twice that diameter. Less and less exist of the stronger nodes. Nodes are immobile, and grant spells according to their Class (1 being the weakest).
Faerzress: Pockets of magical radiation. It isn’t harmful, but Drow value these areas and try to build in them. They tap the fields for unique experiments, and create items powered by it which are cheaper, and do not work outside of the area. Complicates/prevents magical teleportation, as well as magical scrying and divination. Sometimes infuses creatures…