Alchemical Golem

Acidic Membrane. Whenever the golem is hit with a melee attack that deals at least 10 piercing or slashing damage by a creature within 5 feet of it, the golem's membrane ruptures. The attacking creature is splashed by the golem's chemicals and takes 9 (2d8) acid damage. A creature also takes this damage upon making physical contact with the golem, up to once per round.

Collapsing Membrane. When the golem dies, its membrane falls apart, and the surrounding area is drenched in chemicals. All creatures within 15 feet of the golem when it dies must make a DC 16 Dexterity saving throw or take 22 (4d10) acid damage on a failed save, or half as much on a successful one.

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.

Neutralization Weakness. Whenever the golem is targeted by a spell or magical effect that cures the poisoned condition, such as lesser restoration, the golem gains disadvantage on all its attacks, and creatures have advantage on the saving throw of its Acid Breath attack, until the end of its next turn.

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

Multiattack. The golem makes two slam attacks.

Slam. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage plus 4 (1d8) acid damage.

Acid Breath (Recharge 5-6). The golem sprays chemicals in a 15-foot cone. Each creature in that area must make a DC 16 Dexterity saving throw, taking 27 (8d6) acid damage on a failed save, or half as much damage on a successful one.