Gray Dwarf (Duergar)
From D&D 5e
In cities deep in the Underdark live the duergar, or gray dwarves. These vicious, stealthy slave traders raid the surface world for captives, then sell their prey to the other races of the Underdark. They have innate magical abilities to become invisible and to temporarily grow to giant size.
Sources:
- Player’s Handbook, p. 20