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

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

Magic Weapons. The golem's weapon attacks are magical. Even within its own antimagic field.

Unstable Antimagic. The golem is surrounded by a 30-foot radius area of antimagic, as in the antimagic field spell. At the start of each of the golem's turns, roll a d6. On a 1, the antimagic field is disabled until the start of the golem's next turn. While the antimagic field is disabled, the golem absorbs power from any magic cast upon it. Any spell of 1st level or higher that targets the golem or includes the golem in its area of effect is absorbed in this way. When the antimagic field becomes enabled again, the golem first release a burst of force. Each creature within 30 feet of it must make a DC 23 Dexterity saving throw. A creature takes force damage equal to 1d8 per slot level absorbed on a failed save, or half as much damage on a successful one.

Multiattack. The golem makes two melee attacks and uses it stomp once.

Slam. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 25 (3d10 + 9) bludgeoning damage.

Punt. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 18 (2d8 + 9) bludgeoning damage.

Stomp. The golem jumps up a few feet into the air before stomping back down. An area of ground extending 10 feet out from the golem becomes difficult terrain, and each creature within the area must make a DC 23 Dexterity saving throw. A creature takes 22 (4d10) bludgeoning damage on a failed save, or half as much damage on a successful one. If the ground the creature was standing on was already difficult terrain before the golem stomped, the damaged roll is increased to 33 (6d10) for that creature as the losse rubble further bludgeons it. 

The golem can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The golem regains spent legendary actions at the start of its turn.

Attack. The golem makes one attack.

Detect. The golem makes a Wisdom (Perception) check.

Jumping Strike (Costs 3 Actions). The golem jumps to a point within 15 feet of it without provoking opportunity attacks, causing the same effect as its Stomp action at its destination.