The first Drow were refugees of a long forgotten between mortal kind and Dragons. The “Dragons’ Sow” as they were called, were essentially a cult which worshiped the Dragons. Their name came from the ritual sacrifice of some of their people every year to appease their dragon overlords.
When the war had begun, they were used as foot soldiers by their dragon overlords. Due to the immense disparity in technology, however, they were slaughtered on the battlefield even while their masters struggled to control the skies. Many of them were happy to lay down their lives, believing that the dragons would lead them to salvation. But as their culture neared extinction, some realized that their masters could not prevent annihilation. And so they fled, deep into the cave systems below the earth.
They had another name for themselves once, but perhaps in acknowledgement of the folly in willingly following those brutal, inhuman creatures, they took on the derogatory name the ancient people had used for them. Over millennia, this was shortened to “Drow”. Their skin became darker to blend in with the gloomy caverns they now called home, their eyes reddened as their darkvision improved. Their silver hair comes from a bloodline curse willingly taken by the first Drow. Their ancestors had beautiful, prismatic hair granted by the dragons which shone with all the colors of the rainbow. When they abandoned the dragons they abandoned this, and a powerful Drow wizard leeched the hair color from all Drow and their descendants.
As millennia passed, they spread out across the Underdark. While their brutal warfare was no match for the ancient civilizations, it was a match for the creatures living down in the darkness. Even so, a warrior culture emerged of necessity. Every Drow was trained from birth to wield a sword and magic, and slowly but surely they began to colonize the vast unknown.
The primary trappings of Drow society today are spartan living, martial prowess, and a hatred of dragons. The first comes from the harsh conditions of their ancestors. There was not much to go around at first, and so everyone lives with only the necessities. There are a few luxuries like art and culture, but these are done in the spare time of warriors and tradesmen as stress relief. As such, their art is often as brutal as their situation, their songs mostly battle-hymns and funeral marches. The second comes from their constant struggle to survive against the Underdark, which boasts some of the most dangerous monsters in all of Embris. The last comes from their origins, when they lost their innocence as a society and realized that the gods they worshiped are no longer gods at all.
That is not to say that they do not worship at all, however. Following trade with the races who came later, they acknowledge the existence of the major gods, and almost all Drow pay homage to one or more. The most common are Valewind because the Drow believe it is their birthright to explore all of the Underdark, Leontari because of their warrior culture, and Cosantoir for the protection he provides their bastions of civilization. They do not pay any respect to Luna and Solis, however -- the moon and sun never shine on the world below.
Duergar (lit. “Deep Dwarves”, from Dwarvish) are both a peaceful race and among of the greatest weaponsmiths in all of Embris. Their ancestors were a clan of Dwarves which are rumored to have lived in the Gurui Plateau before its fall. The miners and craftsmen of the ancient nation, the Duergar were designers of some of the most powerful weaponry the surface had ever seen. But when the war happened the Duergar were driven under ground by some means, and were never seen by the surface dwellers of that time again.
The Duergar had high hopes for the new world below their feet. They imagined an uninhabited place where there would be no need to make weapons to survive. Imagine that, a society unarmed. True peace. They were shocked by what they found. Deadly creatures, some of which could rival even the dragons. And so, with a heavy heart, they got back to work doing what they did best. They had to make do, and so their technology went from light rifles and plasma cannons back to swords and bows, but with the quality of their smithing, it was more than enough. They built a city, armed the people, and set out conquering the Underdark.
Over the generations, they began to change. Their skin and hair darkened, their darkvision improved, and they awoke innate magic which allowed them to grow larger to combat greater threats. After a few centuries they met the Drow. After a brief struggle to communicate (both sides had forgotten the Common language due to the homogeneity of their communities), they developed a new language, Undercommon, to speak to each other. What followed was an alliance, where the Duergar provided the Drow with weapons, allowing them to conquer and explore the more dangerous reaches of the Underdark themselves. The Duergar followed in their wake, settling in the Drow-cleared areas which were more suitable to Dwarven settlement than Elven.
Thus, they managed to somewhat achieve their dream. The only weapons the Duergar keep for themselves are those of self-defense. There is little violence inside the walls of their cities, most of it committed by the outsiders who come to trade. Their culture flourishes in spite of the harsh environment, and their belief in their patron god, Sifyri, is strong. He guides their hammer, which down in the world below, can be said to be the hammer of civilization itself.
The Dark Gnomes are an evil race of creatures who despise the surface and all who reside there. Their ancestors were a society of Gnomes who revered Solis, god of the Sun. After betraying him, they were cursed to be weakened by Solis’s light, and so they retreated into the Underdark. Once there, they created a twisted society which reveres the foul creatures of the depths, and which harbors nothing but hate for the denizens of their previous home.
Once, the Dark Gnomes were a kindly race which revered Solis. When Solis was young, they would laugh and play. When Solis was an adult, they would wage righteous battle against evil in the world. When Solis was old, they would give out advice to other communities and help guide them on the right path. Over the centuries, however, these Gnomes began to question the virtue of this endless cycle. They wondered why the ebb and flow of their lives was dictated by the growth and rebirth of the sun. Why would they fool around even when important work was to be done, just because Solis was playing around? Why would they fight and die to appease this capricious being? Over time, these sentiments grew, and they turned their back on Solis. They did not do anything so extreme as tearing down his temple, but they decided to make their lives their own.
Perhaps out of foolishness, or more likely (for none knew Solis better than they) out of spite, they did this when Solis was at his most irate. Solis took deep offense to their betrayal, and so his light shone harshly on them and their descendants, cursing them to live in the dark. The surface became inhospitable for their kind, and they headed down into the Underdark to escape Solis’s wrath.
Life was hard at first, and the struggle to survive led the Dark Gnomes to curse the surface-dwellers, who were allowed to live in comfort, all the more. But as years turned to decades, the Dark Gnomes carved out a place for themselves. They found kindred spirits in the Drow, the Duergar, and the other people who made their homes down in the dark, although no race (even those native to the world below) held so much animosity towards the surface as the Dark Gnomes did.
Above all, the Dark Gnomes value independence. The ability to choose one’s own destiny is paramount to these people, who gave up everything for it. All manner of professions are practiced and encouraged, so long as it is what the practitioner wishes to do. Dark Gnomes often fill niches in Underdark communities, rare professionals in obscure fields such as medicine or gemcraft.
For religion, some filled the void left by Solis with worship of other Deities, most notably Fideleé. They do not make such lofty pledges as the one made to Solis, but they still revere the divine as long as the divine gives them the space to pursue their hearts desires. Others, however, turned their back on religion entirely. They believe none of the gods are to be trusted, and would even be willing to burn down temples and destroy idols if it didn’t mean restricting the right to choose of the worshippers.
The Quaggoth consider themselves to be the rightful rulers of the Underdark. When the first humanoids were born, the first Quaggoth were born in the Underdark. They tamed the wild caverns of their home, and they made the Underdark their home. Now, millennia later, they have been turned into a nomadic group of hunter-gatherers, shadows of their former selves slowly being hunted to extinction by the vengeful descendants of the refugees they spurned.
Although their initial conquest of the most inhospitable environment in all the Material Plane was grand, it is little more than a legend these days. They fought against all manner of foul creatures to carve out a place for themselves underground, and from there they decided to expand. All of this dark place was theirs for the taking, at least until the Drow came.
The Drow were simply looking for a place of refuge, a place to rebuild. The Quaggoth told them to go back where they’d come from. When the Drow refused, war ensued. But the Quaggoth were used to fighting monsters and madness. The Drow had just fought a war against a powerful ancient empire. Despite their huge advantage in numbers and territory, the tactics and technology of the Quaggoth left much to be desired, and so the Drow slowly gained ground.
Matters only worsened when the Duergar came. Rather than learning from their mistakes, the Quaggoth attempted to expel them as well. The Drow and Duergar joined forces, and the situation became even worse for the Quaggoth as their once proud society was slowly ground to dust in the onslaught of time. Their foes held no remorse, seeing them as little better than the other beasts that lived down in the darkness.
After yet more millennia passed, the last of the Quaggoth settlements was razed. The Quaggoth survived by escaping into the harshest parts of the Underdark, but even now as the Drow and Duergar attempt to tame these lands, their numbers dwindle and they run out of places to hide. They live now a race of nomadic warriors, ever-cursing the people who took what was theirs and show no intention of stopping.
The Quaggoth know of the gods, but they curse them as foreign invaders just like the Drow and Duergar. They believe only in their own strength, despite how it has failed them over the years. Their stories are passed down through word of mouth, and so their history will be remembered until there are no more Quaggoth to remember it.
The Kuo-Toa are native to the huge underground oceans and lakes of the Underdark, residing in massive underwater cities to avoid competition with the many sapient races that dwell in the dry caves. Thanks to their weakness (both real and perceived) the most important thing to a Kuo-Toa is avoiding conflict with greater creatures, and so they are always polite in their own way.
Kuo-Toa are native to the deep waters of the Underdark, and have lived down in the world below for as long as the Quaggoth. When the two met, the Quaggoth realized the impracticality of conquest, and so they simply demanded tribute from the hapless Kuo-Toa, who were happy to oblige as long as it meant there wouldn’t be a fight.
When the Drow began their bloody conquest, the Quaggoth demanded assistance. Naturally, the Kuo-Toa refused. In fact, recognizing who was in charge, they began giving their tribute to the Drow, exchanging one master for another as naturally as one would exchange hats. The Quaggoth cursed them for their insolence and cowardice, but already fighting a losing war, they were powerless to do anything about it. The Drow were happy to accept this newfound support, although it took many years before they understood what the meaning behind the gifts of the Kuo-Toa were.
Kuo-Toa have no particular strengths or weaknesses when it comes to production and trade. They have many members capable of fulfilling any roles, though their mining is a bit hampered due to the difficulty of mining underwater. They do inhabit some islands in the deepest reaches of Underdark seas, though these places are kept secret to all but the Kuo-Toa. As far as other creatures are concerned, Kuo-Toa civilization exists solely beneath the waves.
For religion, the Kuo-Toa create their own deities. Literally. The power of their belief is so strong that it can create extremely powerful beings based on their religious practices and beliefs. If a city of Kuo-Toa believes in the existence of an almighty six-armed gorilla that breathes fire, such a being will spring into existence and answer their prayers. If enough Kuo-Toa believe that a being that already exists is divine, that being will gain power that befits a demigod. As such, there are many different deities in Kuo-Toan society.
Despite looking like crazy Dwarves, Derro are actually their own race of humanoids. They are not native to the Underdark, but no one in the Underdark knows where they came from. They sort of just showed up one day and started spreading out. They lack the wherewithal to create their own societies, so they usually mingle with other Underdark civilizations which tolerate them.
The Derro have no conception of their own history or culture. Their cognition is extremely warped, leading to eccentric behavior in the best of cases. Most Derro live their lives on bizarre whims, finding strange goals they seek to fulfill, often to their own detriment. Nevertheless, they understand enough about the world to follow society’s rules for the most part, ensuring their continued existence in the strange niche they have created for themselves.
There is no creature more feared by sapient life in the Underdark than the Mind Flayers, or Illithids as they are called in Undercommon. Rapacious brain-eaters, Mind Flayers are as likely to crush a city in one fell swoop as they are to slowly poison it from within, turning the inhabitants against each other in an excruciating process of self-destruction. While the creatures of the Underdark who came as refugees from the surface have clear origins, the origins of the Mind Flayers are shrouded in mystery.
The first Mind Flayer was a being born in the Endless Dark. It felt an intense hunger for knowledge, and this hunger became very literal. It scoured the far reaches of the Astral Sea to sate its hunger, but it found the bounty in that desolate place wanting. It drew upon its psionic energy, performing a ritual which resulted in it being transported in the deepest part of the Underdark. Once there, it found sapient creatures to feed on, and it reached the next stage of its evolution and became an Elder Brain. It spawned its own colony, and from that colony many Ulitharids who would become Elder Brains of other colonies spawned, spreading the race across the darkest depths of the Underdark and beyond.
It is impossible to discuss Mind Flayer society without beginning with the Elder Brain. Each colony of Mind Flayers is a hive mind controlled by an Elder Brain. A Mind Flayer in a colony has very little will of its own, and is completely subordinate to the will of an Elder Brain. A healthy Elder Brain, properly functioning, views itself as the absolute ruler of its small demesne, and it is perfectly comfortable with this role. It has no aspirations of conquest, and indeed were it not for its need (and the need of its subordinates) to consume sapient brains, an Elder Brain would be perfectly content to mind its own business. Unfortunately for the sapient creatures of the Underdark, it possesses such a need, and so Mind Flayers are sent out to hunt from time to time. These hunts are almost always successful, but they never take more subjects than they need to sate their hunger. Not all Elder Brains hunt to survive, however -- some rear humanoids as livestock, and live in completely insular communities.
Ordinary Mind Flayers, kept in check by an Elder Brain, are not the ones dreaded by Underdark civilization. An Elder Brain has no reason to destroy entire cities, and doing so would be counterproductive, since the more sapient creatures there are nearby, the easier it is to procure a meal. It is the Mind Flayers with no master that are the greatest threat. An unbound Mind Flayer believes itself to be the pinnacle of creation, and it believes it should rule over all others. These Mind Flayers go out of their way to attack humanoid settlements, enthralling the people within or simply wiping them out, depending on their whim. Some Mind Flayers even band together, though these alliances tend to be short-lived due to the arrogance of the members.
For Mind Flayers in a colony, their ‘religion’ is complete subservience to the Elder Brain, who they view as the beginning and the end of all things in their lives. For Mind Flayers outside a colony, they believe themselves the superiors of even the gods, and so they worship nothing but themselves.
Like Mind Flayers, Aboleth are creatures of the Endless Dark. The progenitor of all Aboleth was a voracious being which sought to devour all sentient life and become a living record of everything that was. It came down from the Endless Dark into the oceans of the material plane, where it began its consumption.
It formed a massive undersea empire, and its servitors brought all manner of creatures for it to consume. Cosantoir took notice of this, and he led a party of heroes into the deep sea to defeat the Aboleth. Their battle was fierce, but it ended in Cosantoir’s victory. Unable to truly kill this ancient being, Cosaintor cast it into the depths of the world, where it could do little harm to the surface.
While the Mind Flayer can absorb the knowledge and experience of its victims, the Aboleth does so with memory. Any creature consumed by an Aboleth has its memories of both its current life and its past lives absorbed by the creature. Furthermore, Aboleth contain a racial memory. They possess all the memories of their progenitors. Because all Aboleth are descendants of the first, they all remember the battle with Cosaintor and their exile. They seek to one day return to the surface and create their dominion anew, but for now they bide their time.
Aboleth are solitary creatures. They live in deep pools and use their powers of mental dominion to create slaves called servitors. The servitors carry out the will of the Aboleth while living in bliss. Anyone caught by an Aboleth experiences their deepest desires day in and day out while in the Aboleth’s care.
Kruthiks were created by an ancient empire ruled by a powerful Damned. Essentially an alchemical hybrid (like a Chimera), Kruthiks are a combination of drakes and a burrowing insect native to the Hells. They were initially used as siege weapons to undermine static fortifications. When the empire fell, however, the Kruthiks escaped, and burrowed down into the Underdark.
The methods to control Kruthiks have been lost to time, and now, they are an unyielding force of chaos and destruction down in the World Below. All races, from Drow to Duergar to even Mind Flayers, fear their wanton rampages. As such, Kruthik extermination is taken very seriously, and is a thriving industry in most Underdark civilizations. There is an entire guild called the Bug Catchers dedicated to the elimination of Kruthiks, and over the millennia they have built up a great deal of knowledge and expertise in that practice.