Adamantine Casing. The Adamantine Warrior is unaffected by critical hits.

Siege Monster. The Adamantine Warrior does double damage and always deals critical hits to structures, and can pass through structures with under 100 HP by taking a dash action through the structure.

Fist. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 10 (1d8 + 6) bludgeoning damage.

Maul. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 19 (2d12 + 6) bludgeoning damage.

Shoulder Cannon. Ranged Weapon Attack: +3 to hit, reach 60/300 ft., 1 target. Hit: 21 (3d10 + 6) bludgeoning damage, and the target must succeed on a DC 17 Strength saving throw or be knocked prone.

Trample. The Adamantine Warrior takes a dash action. Any creatures caught in this must make a DC 17 Dexterity saving throw or take 24 (6d6+6) bludgeoning damage, and be knocked prone.

The Adamantine Warrior can take three legendary actions per round, and only at the end of another creature's turn. The Adamantine Warrior regains spent legendary actions at the start of it's next turn.

Stomp (Costs 1 Action). The Adamantine Warrior stomps the ground with ground-shaking force. All creatures that are within 15 feet of the Warrior and not in the air must make a DC 17 Dexterity saving throw or fall prone

Reckless Swing (Costs 2 Actions). The Adamantine Warrior spins in circles, wildly attacking whoever is close. The Adamantine Warrior makes a weapon attack with whatever it has equipped, but the attack roll is applied to every creature within 5 feet of it. If this hits a creature, they must succeed on a DC 17 Strength saving throw or be pushed back up to ten feet. If the Adamantine Warrior fails to strike anyone with this attack, all attacks against it the following turn have advantage.