Duergar
Like other dwarves, duergar were typically thick, stocky figures, though beyond this there were many differences. Both male and female duergar were typically bald, with females also lacking the capacity to grow facial hair. Many were also thinner than their dwarven brethren. Most obvious, however, was their dull gray skin and hair, often matched with an equally stolid expression. Regular dwarves said they had flat heads, possibly as an insult.
Tyrannical, grim, industrious and pessimistic, the lives of the gray dwarves were bleak and brutal. Rather than a flaw, however, they viewed their lack of happiness as their greatest strength, the defining feature of duergar pride. The duergar saw themselves as the true paragons of dwarvish ideals compared to their weak and pampered kin, but in truth, their ways were a dark reflection of those found in normal dwarves.
Duergar were, as a whole, generally cruel and malevolent creatures, but as in most evil races this was as much a cultural affectation as a psychological trait.Duergar would often ferment fire lichen into their alcoholic beverages, to create a hot and spicy drink.
During their captivity, which lasted for generations, the mind flayers performed many cruel and unusual experiments on the dwarves. It was during this harsh period of their history that the duergar emerged as a distinct subrace. Eventually, they rose up against their captors and gained their freedom from the mind flayers.
For More info: DND players handbook

Comments