Caustic Golem

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

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

Corrosive Form. A creature that touches the golem or hits it with a melee Attack while within 5 feet of it takes 4 (1d8) acid damage.  Any nonmagical weapon made of metal or wood that hits the golem corrodes.  After dealing damage, the weapon takes a permanent and cumulative -1 penalty to Damage Rolls.  If the penalty drops to -5, the weapon is destroyed.  Nonmagical Ammunition made of metal or wood that hits the pudding is destroyed after dealing damage.  The golem can eat through 2-inch-thick, nonmagical wood or metal in 1 round.

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

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

Volatile Components. If the golem takes fire damage, a small explosion is triggered, dealing 22 (4d10) fire damage to the golem.  Creatures within 5 feet of the golem must make a DC14 Dexterity saving throw, taking 11 (2d10) fire damage on a failed save.

Toxic Sight. The golem can see any creature or object within 240ft currently covered in any source of filth, grime, dirt, or poison, even behind total cover.

Multiattack. The golem makes two slam attacks.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (1d10 + 5) bludgeoning damage and 11 (2d10) acid damage. If the target is a creature, it must succeed on a DC 15 Constitution saving throw or have its hit point maximum reduced by an amount equal to the acid damage taken. The target dies if this attack reduces its hit point maximum to 0. The reduction lasts until removed by the greater restoration spell or other magic.

Haste (Recharge 5–6). Until the end of its next turn, the golem magically gains a +2 bonus to its AC, 30 ft. of movement, and has advantage on Dexterity saving throws, and can use its slam attack as a bonus action.

Acid Spray (1 Use). The golem exhales acid in a 15-foot cone. Each creature in that area must make a DC 19 Dexterity saving throw, taking 45 (10d8) acid damage on a failed save, or half as much damage on a successful one.  In addition, nonmagical armor worn by affected creatures are partly dissolved and take a permanent and cumulative -1 penalty to the AC it offers.  The armor is destroyed if the penalty reduces its AC to 10.

The Caustic Golem can take 2 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 Caustic Golem regains spent legendary actions at the start of its turn.

Corrode. The golem makes a Slam attack.  On a hit, this attack deals an extra 11 (2d10) Acid damage.  This damage is included in the calculation of hit point maximum reduction.

Reload. If the golem currently has 0 uses of its Acid Spray ability, it may move up to its speed toward the nearest Ooze.  This movement does not trigger opportunity attacks.

Devour Ooze (Costs 2 Actions). The golem targets an Ooze in an adjacent space, triggering the Ooze's Split ability if it has one, and regains 38 (4d10+16) hit points, destroying one of the Ooze's two new forms in the process.  The golem regains one use of its Acid Spray ability.