Adamantine Golem

The adamantine golem's slam attacks score a critical hit on a 19 or 20, and if the target is wearing nonmagical metal armor, its armor is damaged and takes a permanent and cumulative −1 penalty to the AC it offers. The armor is destroyed if the penalty reduces its AC to 10.

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

The adamantine golem is immune to any spell of 5th level or lower.

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

The adamantine golem's weapon attacks are magical.

The adamantine golem regains 10 hit points at the start of its turn. It can only be permanently destroyed if reduced to 0 hit points and then decapitated using an adamantine weapon—alternatively a wish spell can be used to slay it while it is at 0 hit points.

The adamantine golem makes two slam attacks.

Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 23 (2d12 + 10) bludgeoning damage.

The adamantine golem moves up to its speed.

The adamantine golem makes a slam attack.

The adamantine golem moves up to its walking speed and targets each creature within 5 feet of it during its movement. Each target must succeed on a DC 18 Dexterity saving throw with disadvantage or take 29 (3d12 + 10) bludgeoning damage. Until the start of its next turn, all attacks against the adamantine golem have advantage.