Alchemical Infusion. Syringes on the golem’s back pierce its silver hide and infuse it with a powerful admixture. At the start of its turn, the alchemical golem can select one of the following infusions. Each infusion lasts until the start of its next turn. The golem can’t use multiple infusions at once.
Brimstone: The golem takes 7 (2d6) 2d6 necrotic damage when it activates this infusion. The golem can breathe poison as an action. In addition, any creature that starts its turn within 5 feet of the golem must succeed on a DC 16 Constitution saving throw or be poisoned until the start of the creature’s next turn.
Quicksilver: The golem takes 14 (4d6) 4d6 necrotic damage when it activates this infusion. The golem’s silver hide turns to shifting quicksilver, increasing its speed to 40 feet and granting it resistance to damage to which it is not already immune.
Salt: The golem takes 17 (5d6) 5d6 necrotic damage when it activates this infusion. The golem’s silver hide is covered with salt crystals, increasing its AC by 3. The golem’s slam attacks deal an extra 14 (4d6) piercing damage and the ground within 20 feet of the golem becomes difficult terrain for 1 hour.
A creature can force an adamantine syringe into the golem’s body with a successful DC 25 Strength check while grappling the golem, nullifying its current infusion and dealing 35 (10d6) 10d6 piercing damage to it.   Elemental Expulsion. Whenever the golem takes acid, cold, fire, or lightning damage, all creatures within 20 feet of the golem must make a DC 16 Dexterity saving throw, taking damage equal to the damage the golem took on a failed save, or half as much damage 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.