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.

Reactive. The adaptable golem can take one reaction on every turn in a combat. Additionally, effects that would prevent the golem from taking reactions only last for one turn instead of the stated duration.

Multiattack. The golem makes two slam attacks or vents its core.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 5) bludgeoning damage.

Vent Core. The golem opens its armored plating and vents its core, unleashing energy that has been absorbed in a 20 ft radius around it. If the golem has gained resistances or immunities from the Adaptable Resistance and Adaptable Immunity reactions, it can choose to lose up to four resistances or immunities, augmenting this ability's damage based on the resistances or immunities vented.

All creatures in that radius must make a Constitution saving throw (DC 15) or take damage based on resistances and immunities vented on a failed saving throw, taking half damage and suffering no secondary effects on a successful saving throw.

The damage from multiple resistances or immunities add together, but only one secondary effect can be applied, which the golem chooses from the resistances or immunities vented.

Vent Acid. Venting acid resistance or immunity causes this ability to deal 1d10 acid damage (2d10 if the golem has immunity to acid damage) and reduces the creature's AC by 2 until the end of their next turn as acid sprays throughout the area.

Vent Bludgeoning. Venting bludgeoning resistance or immunity causes this ability to deal 1d10 bludgeoning damage (2d10 if the golem has immunity to bludgeoning damage) and knocks the creature prone as globs of the golem's armor are shot out and drawn back in.

Vent Cold. Venting cold resistance or immunity causes this ability to deal 1d10 cold damage (2d10 if the golem has immunity to cold damage) and reduces the creature's speed by 10 feet until the end of their next turn as the area is flash-frozen.

Vent Fire. Venting fire resistance or immunity causes this ability to deal 1d10 fire damage (2d10 if the golem has immunity to fire damage) and the creature takes an additional 1d6 fire damage at the start of their next turn as white-hot flames scorch the area.

Vent Force. Venting force resistance or immunity causes this ability to deal 1d10 force damage (2d10 if the golem has immunity to force damage) and incapacitates the creature until the end of their next turn as a wave of arcane force reverberates through the area.

Vent Lightning. Venting lightning resistance or immunity causes this ability to deal 1d10 lightning damage (2d10 if the golem has immunity to lightning damage) and prevents the creature from taking reactions until the end of their next turn as lighting arcs and crackles through its body.

Vent Necrotic. Venting necrotic resistance or immunity causes this ability to deal 1d10 necrotic damage (2d10 if the golem has immunity to necrotic damage) and reduces the creature's hit point maximum by half the necrotic damage taken as blighting energy drains its life force. The reduction lasts until the target finishes a short or long rest. The target dies if this effect reduces its hit point maximum to 0.

Vent Piercing. Venting piercing resistance or immunity causes this ability to deal 1d10 piercing damage (2d10 if the golem has immunity to piercing damage) and restrains the creature until the end of their next turn as they are impaled by mercurial spikes.

Vent Radiant. Venting radiant resistance or immunity causes this ability to deal 1d10 radiant damage (2d10 if the golem has immunity to radiant damage) and blinds the creature until the end of their next turn as blinding light pours from the core.

Vent Slashing. Venting slashing resistance or immunity causes this ability to deal 1d10 slashing damage (2d10 if the golem has immunity to slashing damage) and the creature takes an additional 1d6 slashing damage at the start of their next turn as fragments of the golem's body shoot out as blades.

Vent Thunder. Venting thunder resistance or immunity causes this ability to deal 1d10 thunder damage (2d10 if the golem has immunity to thunder damage) and deafens the creature until the end of their next turn with a thunderclap.

Adaptable Resistance. The golem has been designed to adapt to damage, rendering itself much harder to destroy. When damaged by a damage type that it is neither immune nor resistant to, the adaptable golem can use a reaction to become resistant to it.

Adaptable Immunity. When damaged by a damage type that it is resistant but not immune to, the adaptable golem can use a reaction to become immune to that damage type.