Destructive Force. Whenever an adamantine golem scores a critical hit it can roll additional damage dice.

Fire Absorption. Whenever the golem is subjected to fire damage, it takes no damage and instead regains a number of hit points equal to the fire damage dealt.

Immutable Form. The golem is immune to any spell or effect that would alter its form.

Indestructible. Even if reduced below 0 hit points its potent healing abilities continues to restore hit points, though the golem is unconscious and incapacitated unless above 0 hit points. After 1 minute the golem is restored to half it's hit points. It can only be permanently destroyed if reduced to negative hit points and then decapitated using an adamantine weapon—alternatively, wish can be used to slay it while it is at negative hit points.

Also, any critical hit against the golem becomes a normal hit.

Magic Resistance. The golem has advantage on saving throws against spells and other magical effects.

Magic Sense. The golem can automatically pinpoint the direction and origin of spell effects, even from invisible creatures.

Magic Weapons. The golem's weapon attacks are magical.

Multiattack. The golem makes two melee attacks.

Slam. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 22 (3d8 + 9) bludgeoning damage.

Arcane Armament (Recharge 6). The golem fires a potent blast of magical energy at a target it can see within 300 feet. The blast of magical energy explodes upon impact in a 30-foot radius around the target. All creatures in the blast radius, along with the creature hit by the impact must succeed on a DC 17 Dexterity Saving Throw or take 44 (8d10) force damage, or half as much on a success.