Siege Monster. The hammerer deals double damage to objects and structures.
Multiattack. The hammerer makes one Claw attack and one Hammer attack.
Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit:6 (1d6 + 3) piercing damage.
Hammer. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit:10 (2d6 + 3) bludgeoning damage.
Engine of Pain. Immediately after a creature within 5 feet of the hammerer hits it with an attack roll, the hammerer makes a Hammer attack against that creature.
Creative duergar engineers have built numerous war machines, including some that can be fused with a duergar. Such a duergar-machine hybrid is fueled by the duergar's psionic energy, and the duergar inside the machine can psychically channel pain into power when attacked.