Before the hill dwarves split from the original mountain dwarves, there was a plague, which devastated the dwarven clans. While largest of the clans managed to survive and recover, the Duergar Clan were not so fortunate. The plague, a terrible one which turned their very people against them, spread further and further, and the Duergar found that their only way to escape was to dig deeper. For centuries they dug to escape the plague, until they broke into a massive cavern system, deep, deep underground, which they came to call the World Cavern. After generations of being underground, this clan knows nothing else. Known to other races in the World Caverns as the Duergar. They know no humour or joy and live in constant fear and toil.
Duergar are much taller and thinner than their surface kin, almost as tall as humans. They average about 5 ft tall. They have dusky grey skin, and usually their hair is an identical ash grey. Sometimes the magic in the World Cavern affects the Duergar, and their hair turns a vibrant red, and sometimes a Duergar might be born (regardless of hair color) with glowing hair, as if it were made of embers. These Duergar are often believed to have a grand destiny before them, and many rise to become beings of quite influential positions.
Many of their kind have been affected by their time in the lightless depths, dealing with arcane horrors and aberrations. Some have developed powerful minds and some have been broken by the constant stress, devolving into mad creatures.
The Duergar Clan has several subclans, including the Oremantle, Blackbellows and Ironlight.
Major language groups and dialects
Duergar dwarven is more guttural, and old. It sounds very much like ancient dwarven, and is hard to understand for upworlders. Duergar do not speak common, and instead speak an ancient language that diverted from what is today's common thousands upon thousands of years ago, called undercommon by the upworlders, but called the Ancient Language by thsoe dwelling in the World Caverns.
Culture and cultural heritage
Older legends still exist, but the Duergar often speak bitterly about the upworlders, feeling abandoned and left for dead by them.
Shared customary codes and values
The Duergar share values with the ancient Mountain Dwrves, and one can find several similarities in Duergar rites, daily proceedures and pleasantries.
The largest differences comes from the Duergar having adapted to life in the World Caverns; They are far less conversational, and often keep to themselves. They still greet those they consider friends, or part of their family or clan, but it's simply a mere nod.
Common Etiquette rules
Acknowledging, but respecting the personal space of your peers is very important in duergar society.
More than the other dwarves, individuality is very strong in the Duergar society. Loyalties to one's clan are not as strong, and it's seen more as a mutually beneficial contract. It's not unusual for a Duergar to switch between families.
Properly relaying information and notices to your peers is extremely important to the Duergar; Though a lot of the original group mentality of the dwarves has been lost to the ages, respect and proper societal civility is still required and expected.
Common Dress code
Duergar dress in clothes extravagantly dyed from all the strange plants growing in the World Caverns. Even armor of their military is colored quite strongly; Certain armor parts colored certain ways display rank.
Art & Architecture
The duergar cities are built into the walls and roof of the Caverns. Very similar to the Thalassan dwarves, but incorporating more utilitarian and militaristic approach, the Duergar construct their houses with as cheap material as possible, only creating reinforced and stronger (and much more expensive) housing when perimeters are set around the city or village, which takes a longer time in the Caverns.