Underdark
Tavern tales across Faerûn’s sunlit lands whisper of the Underdark, a lightless, subterranean realm that is home to fabled races and ancient, unspeakable evil. It is a domain of primeval mysteries and unending war, a hidden world of cruel masters and hopeless slaves, filled with monstrous races that were old before humans were born. It is a dank, dismal place of fungus, rot, and slime. It is a land where a few lucky merchants have found a lucrative trade, but where many more have been slain (or worse) for their effrontery. So dire is the reputation of the Underdark and its denizens that mothers caution their children to behave, lest the dark elves steal them away.
A proper account of the Underdark must include the cold machinations of the hateful illithids, the unwholesome cities of the drow elves who pay homage to the bitter Spider Queen, and the unending servitude of the lesser creatures that fall into the clutches of these two races. Unlike the upper world, where civilization and the light of day protect travelers from horrors, the Underdark holds the promise of deadly peril. Illithids, drow, phaerimms, and aboleths vie for supremacy in its dark tunnels and sunless seas. They fight one another with armies of slaves, terrible and ancient magic, and mind-shattering psionics for control of the encompassing tunnel systems and the extended caverns, vaults, cavities, gaps, and nodes that riddle the earth beneath Faerûn. The Underdark is literally an entire world, most of which is inhabited by monstrous and evil creatures that shun the daylight. Hundreds of independent cities, towns, and strongholds are scattered throughout the caves and caverns that make up this realm.
Tunnels in the Underdark extend for miles, some ballooning into caverns thousands of feet across, only to shrink to spaces too narrow for a halfling to squeeze through. The largest cavern halls are often representations of the surface in miniature, with hills, valleys, underground rivers, and lakes. Most races native to this realm make use of the walls and ceilings of their caverns, accessing the higher levels via natural or magical flight or levitation, or even wall-crawling mounts such as giant spiders and certain breeds of lizards.
The Underdark is divided into three levels. The upper Underdark (Upperdark) is close to the surface, and its residents have considerable interaction with surface races. The inhabitants of the middle Underdark (Middledark) tend to see surface races as potential slaves. The lower Underdark (Lowerdark) is an incredibly strange place filled with alien societies and bizarre cultures hostile to those unlike them.
An Underdark Primer
While many surface dwellers regard the Underdark as all the same (one big cave, infested with hungry monsters), the wise adventurer prepares by studying what surface dwellers know about the Realms Below before venturing underground. Knowing what sorts of creatures and dangers lurk at what depths might mean the difference between life and death. The Underdark is divided into three general levels: The Upperdark, the Middledark, and the Lowerdark.
Exploring the Underdark
What squelches through unlighted corridors miles below the daylit surface world? What secrets of ancient vintage rest behind long-cooled barriers of solidified magma? What perils and terrors await those foolhardy enough to venture into such a dismal and dangerous environment? Adventurers from all over Faerûn dare the depths of the Underdark in search of fame, fortune, and power, but all too often they find only death—or fates even worse than death.
Geology and Environments
A cave is a natural opening in rock that is large enough for creatures to enter. The Underdark, simply put, consists of a linked network of several titanic cave systems. Large portions of it do fit the definition of “a natural opening in rock,” but the Underdark also encompasses areas of deep water that hide coral caves, hollowed-out sections of ice in which creatures live, and places where fungus, bone, or even pure force form “caves.” Underdark terrain is dynamic and changeable. A map drawn a few decades ago may show tunnels that have long since collapsed, or lakes that are now dry. Terrain can change gradually over the course of decades, centuries, and millennia, or swiftly as a result of an earthquake or volcanic eruption.
The Underdark Environment
Walking through wild caves without end is different than stalking monsters in a dungeon near the surface. Travelers venturing into the Underdark enter a world in which nothing can be taken for granted. Vast portions of the Realms Below are wastelands devoid of food, water, and even light.
Spelunking
When traveling in cramped natural tunnels and through narrow, low corridors that vary widely in diameter, it is difficult to move as quickly or fight as efficiently as normal.
Underdark Encounter Tables
The Underdark is a vast region encompassing more square miles than can easily be calculated, especially considering the three-dimensional nature of it. Outside “settled” caverns and vaults, the dark rootways below the mountains and plains of Faerûn constitute a wilderness.
Geography
Faerûn’s Underdark includes drow cavern-cities, sunken aboleth strongholds, entire realms of mind flayers, and wondrous vistas shrouded in everlasting darkness. This chapter describes some of the most notorious, important, and incredible locales in the Realms Below. The locales described here do not represent an exhaustive list of the Underdark realms. Uncounted hundreds—perhaps even thousands—of deeply buried caverns and lightless cities exist beneath Faerûn, and virtually every surface-world dungeon seems to connect to murky depths from which all sorts of horrors can spew forth. Consider the places discussed in this chapter to be the ones that knowledgeable surface folk know of, and a sampling of the types of places that deep-delving heroes might explore.
Underdark Domains
Faerûn’s Underdark is not a single, continuous cavern system, and even places on the same level may not connect to each other. The existence of Underdark settlements beneath Waterdeep and Raven’s Bluff, for example, does not mean that it is possible to travel from one city to the other underground. In fact, the Underdark consists of a number of discrete domains. A domain is simply a collection of Underdark locales among which underground travel is reasonably easy. In certain places it may be possible to trailblaze a route from one domain to another, but then again, it may not. An Underdark domain is something like a large island in the surface world. It may feature several distinct terrains and cultures, but it’s possible to travel all over the island without having to set sail on the ocean. Similarly, two locales in a single domain are connected by enough cave systems, tunnels, and other passages to enable travel from one to the other without leaving the Underdark. Cities and settlements in the same domain are much more likely to engage in diplomacy, trade, or warfare than cities in separate domains. Like the continents or regions of the surface world, domains tend to group disparate cultures together and force them to interact with each other for good or ill. Faerûn’s Underdark consists of seven major domains, a dozen or so minor ones, and hundreds of otherwise isolated locales that don’t appear to connect (at least not easily) to any other Underdark networks. The major domains include the following.
Sites of Interest
The following entries describe cities, ruins, dungeons, and other points of interest that adventurers might wish to visit in the Underdark. A history is given for each, and for some of the more complex areas, descriptions of important sites and NPCs are included.
Each of the following entries includes a parenthetical note about its depth (Upperdark, Middledark, or Lowerdark) and its domain (or geographical region, if it does not belong to a major domain). Unlike surface cities, Underdark cities tend to be monocultural. In many places, anyone who isn’t of the dominant race is either a visitor or a slave. To reflect this arrangement, any city with a sizeable contingent of slaves has a separate notation for the slave population in its community statistics block. The population and racial breakdown of the free residents is given first, and then the slave population. Community assets are calculated from the total population because slaves do help to generate wealth, even if they don’t hold any of it.
Dungeons in the Underdark
A “dungeon” is traditionally located underground, and no part of the Underdark fails to qualify for the term in that respect. For the purpose of adventuring in the Underdark, a dungeon is any locale or extended area that offers the possibility of adventure, danger, and treasure. By this definition, the Underdark contains literally hundreds of dungeons. A few of the most infamous or dangerous are described below.
Citadel of the Fiendish Slayer
Magic of the Underdark
The Underdark eclipses nearly all surface-world locations in terms of the sheer power of its magic and its alien and frightening psionics. Who doesn’t fear the deity-channeled malice and might of Lolth’s clerics? Worse yet are the mind flayers, whose psionic and magical superiority over most other races is as terrifying as their sinister appetites. Less well known, and therefore more mysterious, are the aboleths of the Lowerdark, which harbor secrets of ancient lore within their alien, unfathomable minds.
Beyond what is generally known or rumored, the Underdark shelters a wealth of strange power and magic. The long-hidden deep Imaskari still know spells that leveled kingdoms in ages past. The gloamings and the slyths have abilities that few intelligent creatures (even other Underdark races) understand. And finally, there is the whispered rumor of node magic—a secret lore that allows those with the proper training to channel power from the earth itself.
Lore of the Underdark
Myriad are the paths to power, as the old archmages like to say, and the Underdark is home to at least as many variant types of magic as the surface world. Circle magic, rune magic, and Shadow Weave magic all have their practitioners in the Realms Below. Cooperative circle magic is favored by the grimlocks of Fingerhome. By combining their magical strength, a handful of spellcasters may accomplish things together that even the most powerful of their fellows could not dream of achieving alone. Rune magic is favored by the duergar, particularly in the Underdark city of Dunspeirrin. And the Shadow Weave—the pattern formed by the negative space between the Weave’s strands—is a secretive, shadowy magic that has gained many converts in the Underdark, including the kuo-toa of LoobliShar.
Psionics are even more widely practiced in the Realms Below than they are on the surface. The primary practitioners of such powers are the duergar, the illithids, and the aboleths.
The Underdark also offers one other variant kind of magic that is, for obvious reasons, available only below the earth. This form of power is called node magic.