race features:
Superior Darkvision. Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 120 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern colour in darkness, only shades of grey.
Dwarven Resilience. You have advantage on saving throws against poison, and you have resistance against poison damage.
Dwarven Combat Training. You have proficiency with the battleaxe, handaxe, light hammer, and warhammer.
Tool Proficiency. You gain proficiency with the artisan's tools of your choice: smith's tools, brewer's supplies, or mason's tools.
Stonecunning. Whenever you make an Intelligence (History) check related to the origin of stonework, you are considered proficient in the History skill and add double your proficiency bonus to the check, instead of your normal proficiency bonus.
Psionic Fortitude. You have advantage on saving throws against illusions and against being charmed or paralyzed.
Duergar Magic. When you reach 3rd level, you can cast the Enlarge/Reduce spell on yourself once with this trait, using only the spell's enlarge option. When you reach 5th level, you can cast the Invisibility spell on yourself once with this trait. You don't need material components for either spell, and you can't cast them while you're in direct sunlight, although sunlight has no effect on them once cast. You regain the ability to cast these spells with this trait when you finish a long rest. Intelligence is your spellcasting ability for these spells.
Sunlight Sensitivity. You have disadvantage on Attack rolls and Wisdom (Perception) checks that rely on sight when you, the target of your attack, or whatever you are trying to perceive is in direct sunlight.
Like other dwarves, duergar were typically 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 grey skin and hair, often matched with an equally stolid expression. Regular dwarves said they had flat heads, possibly as an insult.