Armor Class 21 (natural armor)
Hit Points 119 (14d8 + 56)
Speed 25 ft.
Saving Throws CON +8, WIS +6
Damage Immunities poison
Condition Immunities charmed, exhaustion, frightened, paralyzed, poisoned
Senses darkvision 120 ft., passive Perception 12
Languages Dwarvish, Undercommon
Challenge 12
Magic Resistance. The duergar has advantage on saving throws against spells and other magical effects.
Psychic Engine. When the duergar despot suffers a critical hit or is reduced to 0 hit points, psychic energy erupts from its frame to deal 14 (4d6) psychic damage to each creature within 5 feet of it.
Sunlight Sensitivity. While in sunlight, the duergar despot has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.
Multiattack. The despot makes two iron fist attacks and two stomping foot attacks. It can replace up to four of these attacks with uses of its Flame Jet.
Iron Fist. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage. If the target is a Large or smaller creature, it must make a successful DC 17 Strength saving throw or be thrown up to 30 feet away in a straight line. The target is knocked prone and then takes 10 (3d6) bludgeoning damage.
Stomping Foot. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) bludgeoning damage, or 18 (3d8 + 5) bludgeoning damage to a prone target.
Flame Jet. The duergar spews flames in a line 100 feet long and 5 feet wide. Each creature in the line must make a DC 16 Dexterity saving throw, taking 18 (4d8) fire damage on a failed save, or half as much damage on a successful one.
Mordenkainen's Tome of Foes, p. 188