The Duergar live together in cooperative clans, but are technically a collection of several different races - each with their own talents for earth, metal, ore, gems, or soil.

The Badg have large, wide noses, poor eyesight beyond 20ft, limited color vision (red/blue part of the spectrum only), and solid black eyes with hints of blue/purple/gold/brown in the irises (no white sclera.) Their racial talent is with stone, and they are brilliant at civil engineering.

The Rud have eyes and vision like the Badg, although albinism and pure red eyes are slightly more common among their kind. Their noses are longer and their build is just a bit slighter. Their racial talent allows them to easily shape and transform metal and ore, and their craft in tools, weapons, armor, and metallurgy is beyond compare. I've written a short story from the perspective of a Rud Duergar, which you can find here.

The Gnem have eyes and vision like the Badg and the Rud, but their talent is in gems and crystals, and they are masters at making corrective lenses, while also being exceptional tinkerers and scientists. Their noses tend to be hooked and long, and their hair tends towards a spiky and wild look. They are the smallest and least stocky of all the Duergar.

All of the digger races, males and females, have beard whiskers that provide proximity sensation and awareness for navigation underground. They find this very useful in close combat, especially in darkness. Their city folk find it fashionable to braid or shape their beards — or to hang or tie in trinkets — as a display of luxury and social power, but the braids and trinkets are quickly discarded when it’s time to fight.

They spend most of their time underground in "setts," which are incredibly complex tunnel systems, with nearly every inch carved with intricate patterns and markings, and kept perfectly clean. The Duergar value a well-maintained home and a quiet neighborhood.

The Badg are famously unimpressed by anything larger than themselves, don't waste energy on posturing; they just act. To an outsider, Dwarf social life seems devoid of "fluff."

The Badg, in particular, are known for radical honesty: If your plan is bad, they will tell you it’s "shallow-rooted" and walk away. The Gnem are less rude, but still very direct. The Rud are somewhat more capable of politeness and tact, and less naturally avoidant of disohnesty, but they do their best not to alter the Duergar's generally trustworthy reputation.

The Debt of Earth: Trust isn't earned through talk; it’s earned through shared labor. If you want a Dwarf to like you, don't buy them a drink -- help them move a boulder.

Stoic Ferocity: They are quiet until they aren't. An outsider might think a Dwarf is ignoring an insult, only to find the Dwarf has been calmly deciding exactly which of the outsider’s shins to break.

Resource Monopolies: They are fiercely territorial over "their" veins of ore. Trespassing isn't handled with a warning; it’s handled with a shovel to the face.

Being master excavators, their cities wouldn't just be "caves"; they would be organic, defensible labyrinths.

The Blind Gate: They generally don't use much light. To an outsider, a Dwarven city is a terrifying dark maze where the inhabitants move by scent, vibration, and memory.

Low and Tight: In general, dwarven halls aren't grand or airy. They are cramped, circular, and incredibly sturdy. It makes humans feel claustrophobic and elves feel buried alive.

They do have what visitors will call Grand Halls -- vast, cavernous spaces with artistically patterned, high ceilings supported by intricately carved pillars. They're just quarries, where the stone has been pulled away for other purposes.

Vertical Trade: Instead of roads, trade happens via dumbwaiters and hoists. A human tavern might have a literal hole going down from the cellar where empty kegs and full bags of coin come up, to be replaced with full kegs of beer and baskets of bread.

Dwarves don't pay taxes in gold; they pay in Infrastructure.

• Engineering for Ale: A Dwarf will spend years perfectly building a human’s grain mill or building a sophisticated irrigation system just to ensure the barley crop is 10% better. To a Dwarf, a clogged human sewer is a national emergency because it threatens the kitchen.

In setts near remote or rural settlements, the dwarves will maintain a permanent, standing militia to protect the humans. They don't do it out of love; they do it because if the town burns, the beer stops.

While Duergar are often envisioned with shovels and picks and other mining tools, their best and most precise work is done with water and fire. Badg dwarven talent allows them to shape and cut stone near effortlessly with heated, pressurized water, to soften stone in water for reshaping as though it were mere clay, then to harden again in their great kilns. The Rud refine ores into metals like humans make wines or sauces, shape tools as easily as cookies, and layer damascus like human bakers make croissants or baklava. These are all things that require some skill, with some skills being as common as a housewife's favorite muffin recipe, and others being as rare and difficult as a perfect french souffle.

Another slight misconception is that, while Dwarves are known for being long lived, not many outsiders know the how and why of it. The core reason for their reputation for extended lives comes from their ability to voluntarily hibernate for long periods of time. This is a skill mostly practiced by Duergar with a specific need to extend their existence, such as kings and leaders and wise deciders of things and keepers of the histories who slumber when their counsel is not needed. There are also the great teachers and masters of skills that the clans want to preserve, rising once per generation to teach the best of the current best.