Armor Class 17 (natural armor)
Hit Points 33 (6d8 + 6)
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 2
Engine of Pain. Once per turn, a creature that attacks the hammerer can target the duergar trapped in it. The attacker has disadvantage on the attack roll. On a hit, the attack deals an extra 5 (1d10) damage to the hammerer, and the hammerer can respond by using its Multiattack with its reaction.
Siege Monster. The hammerer deals double damage to objects and structures.
Multiattack. The hammerer makes two attacks: one with its claw and one with its hammer.
Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage.
Hammer. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage.
Mordenkainen's Tome of Foes, p. 188