Although dwarves are generally an honorable, straightforward, and fiercely loyal lot, they have their flaws as well. Greatest amongst these flaws is that of greed; dwarves are incredibly avaricious and lust for precious gems and gold like no other race in the world. But even amongst the dwarves, Clan Ranidon was known as an exceptionally avaricious lot. Tireless in their work, they delved deeper and farther into the earth than any other clan ever had in their pursuit of new mines and new sources of wealth. Many historians argue that much of the tunnels Underdark itself was dug out over the course of countless generations by Clan Ranidon in the course of their mining efforts. But in time, even the wealth of the Underdark was depleted by them, and they turned their sights to the deepest layer of the world, which had never before been penetrated: The Elder Earth itself.
Alarmed when he discovered this, then dwarf-king Graven Stonebeard warned repeatedly not to delve into the Elder Earth. He reminded them of the Elder Codex, laid down by the legendary creators and forefathers of the dwarven race. The Codex specifically forbade dwarves from burrowing into the Elder Earth. "All the mountains and the caverns of this world are thine," the Codex promised, "But delve ye not into the world's heart, the Elder Earth, lest the ancient doom consume thee." But Clan Ranidon, confident and arrogant in their great wealth, ignored both the dwarf-king and the Codex. They moved their entire clan into a great city into the Underdark, which they named Gal Ranidon, meaning Ranidon's Home, in preparation for the greatest excavation in all of history. They even gave themselves a new name: Duergar, meaning 'Deep Dwarves'.
Clan Ranidon burrowed into the Elder Earth, and at first, they found priceless gemstones beyond count. Diamonds the size of a dwarven fist, and rubies which gave off a natural, crimson glow in the dark. Elated, they burrowed still further, and there they found their doom. They disturbed a hive of creatures which had never been seen in the world before; strange, bulbous creatures with octopus-like heads who could pluck the very thoughts out of their minds. Terrified by their discovery, Clan Ranidon launched an all out assault and exterminated the entire hive. Despite taking heavy casualties from the creatures' psionic abilities, they heaved a sigh of relief when the battle ended. But unbeknownst to them, the creatures they destroyed had sent a message to the rest of their ilk.
Soon afterwards, their punishment came. These new octopus-headed creatures massed an army and launched a massive retaliatory counter-attack for vengeance on behalf of their murdered kin. Mighty Clan Ranidon was overwhelmed in the twinkling of an eye by these hideous creatures, which they named 'mind- flayers', and hurriedly abandoned Gal Ranidon, trying to flee to the surface, only to find that all of their tunnels had been collapsed. Dwarf-king Graven Stonebeard, in accordance with the Elder Codex, had sealed them in for their defiance of the Codex, grieving as he did so. With no place to flee, Clan Ranidon was doomed. Three quarters of their clan were exterminated, and the remaining quarter was psionically enslaved by these mind-flayers. The mind-flayers took their new slaves and returned to the Elder Earth. For many generations, the remnants of Clan Ranidon remained in servitude to these mind-flayers, who called themselves the illithid. The illithid conducted countless horrific experiments upon the duergar, twisting their mind and toying with the very molecules of their body. It is unlikely that any other race save the dwarves would have survived the experiments, but dwarves are a tough and resilient folk, hardy and resistant. Even so, the enslaved duergar were badly weakened and debilitated as a race from their ongoing torment.
It is likely that the duergar would be enslaved to this very day were it not for an unknown upheaval in the Elder Earth. For reasons which only the illithid know, one day all of their illithid captors simply disappeared, and the mental prisons which they had built disappeared with them.
Battered and broken from their centuries on centuries of mistreatment, the remnants of Clan Ranidon staggered out of their pens and escaped the Elder Earth, retreating to the empty ruins of Gal Ranidon, which they began to rebuild.
This traumatic experience changed the duergar race profoundly. They had been physically transformed by their ordeal, becoming weaker and less hardy than the surface dwarves, yes, but even greater was their mental transformation. Their minds twisted by their torment, they became crueler, distrustful, and more violent. They had become treacherous and backstabbing, and their encounters with the new power in the Underdark which had sprung up in their absence, the foul drow, made them even more so. The duergar had to fend off many drow raiding parties in the early days, often getting the worst of it, until finally an unequal peace treaty was signed between the two civilizations where the duergar would annually send the drow a gift of many precious treasures as well as provide stonemasons who would help decorate and shape drow Houses.
At peace at last, in time Gal Ranidon grew to be a great city once more, rich and wondrousbut neither it, nor its inhabitants, were ever the same, and both the city and its people became dark and cruel.
Duergar possess many similar attributes to surface dwarves. Both are highly resistant to all forms of magic, which stood the duergar in good stead during their centuries of torment. This is speculated to be due to fact that dwarves have an innate connection with the earth and the stone of the world itself, which provide them some protection. They retain the dwarven ability to view the infrared spectrum, borne from long centuries spent underground. They also share the dwarven aversion towards large bodies of water, which are not present in their preferred terrain. Consequently, they are not skilled at fighting on boats or in water, and when they are forced to, do not perform as well as they normally might. In addition, they are more vulnerable than most to water-based attacks, be it magical water-based weapons or the spells of invokers.
The pursuit of wealth is still the overriding goal of almost all duergar, and so duergar society is structured around this as well. Although almost all of the great mines of ancient days have run dry, many lesser mines which Clan Ranidon once disdained are now being cleared and restored to use by the duergar. But since these mines are relatively poor, and they dare not delve into the Elder Earth once more, the duergar have become determined to grow wealthy from another path. Trade. Despite being distrusted and disliked by almost every kingdom, on the surface or elsewhere, the duergar clans have one of the largest trading empires in the world and connections with almost every major city, as their skilled artisans and miners can offer products from the Underdark which no other race, not even the drow, can provide.
Although the duergar can be treacherous and backstabbing, unlike the drow there is surprisingly little backstabbing amongst the duergar themselves, at least within their own clans, although each clan might seek to undermine others so as to gain their wealth for themselves. This is generally considered to be due to the eons-old historical sense of kinship which all dwarves feel for members of their own clans, as well as the group solidarity amongst duergar which was necessary in order for them to survive the torment of the illithid.
The duergar possess a love-hate relationship with the drow. They had many skirmishes in the past, almost all of which went badly for the duergar, until they signed an unequal peace treaty that persists to this very day. By now, the duergar may be strong enough to nullify the treaty, but their aims and drow aims often coincide; in addition, Xymerria is a huge market for duergar goods and services, even if the drow often cheat on their contracts. It is not unknown for duergar and drow to form long-lasting, even permanent partnerships, but a duergar will never, ever, truly trust the drow. Drow, on the other hand, see duergar as occasionally useful allies and servants, but inferiors. Then again, drow view most races in that way.
The duergar also bear a grudge against the surface dwarves, for not coming to their rescue when they burrowed into the Elder Earth. Surface dwarves feel duergar are fools for breaching the Elder Codex; the duergar consider surface dwarves cowards and traitors for not assisting them in their time of need. This resentment is similar to the hatred between elves and drow, although not nearly as profound. The duergar, after all, are still 'deep dwarves', and their relationship with surface dwarves is much akin to that of two estranged brothers; they may rail, rant, and genuinely hate each other, but in the end, will still acknowledge that they are of the same family.
In more recent times, they formed an alliance of convenience with the minotaurs when the former leader of the minotaur Herd, Mahn-Tor, led a powerful force to invade Maelbrim. The duergar made out very well from this venture; they looted many treasures from Maelbrim, were paid handsomely for their support by Mahn- Tor, then were paid even more handsomely by his son, Mahn-Zaar, to abandon Mahn-Tor at the critical point in the war. This has gained the duergar the relative friendship of Mahn-Zaar and the minotaurs, but no small amount of hostility from the locals of Maelbrim.
All other races view the treacherous duergar with suspicion, however, the wealth which they bring to their trading partners makes them generally accepted on the surface, unlike the drow.