AKA gray dwarves, they have ashen skin much like other Underdark races. Duergar are not a happy people; their culture values usefulness and is devoid of the arts. Partners are assigned to ensure the continued survival of their race. They are perfectionists and take pride in their work, often living near volcanoes to accommodate their craft. They have great respect for social order and simply work harder to increase their standing, rather than try to bring down their rivals. If you can't contribute, you have no place in their society.
They frequently trade with other races, but their honor and honesty doesn't apply to outsiders. They won't hesitate to take advantage of others for their own benefit.
One of their main settlements is Gracklstugh, which they begrudgingly share with derro.