Armor Class 15 (natural armor)
Hit Points 38 (7d8 + 7)
Speed 20 ft.
Damage Immunities poison
Condition Immunities charmed, exhaustion, frightened, paralyzed, petrified, poisoned
Senses darkvision 60 ft., passive Perception 7
Languages understands Dwarvish but can't speak
Challenge 3
Engine of Pain. Once per turn, a creature that attacks the screamer can target the duergar trapped in it. The attacker has disadvantage on the attack roll. On a hit, the attack deals an extra 11 (2d10) damage to the screamer, and the screamer can respond by using its Multiattack with its reaction.
Multiattack. The screamer makes one drill attack and uses its Sonic Scream.
Drill. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (1d12 + 4) piercing damage.
Sonic Scream. The screamer emits destructive energy in a 15-foot cube. Each creature in that area must succeed on a DC 11 Strength saving throw or take 7 (2d6) thunder damage and be knocked prone.
Mordenkainen's Tome of Foes, p. 190