Berserk. Whenever the golem starts its turn with 40 hit points or fewer, roll a d6. On a 6, the golem goes berserk. On each of its turns while berserk, the golem attacks the nearest creature it can see. If no creature is near enough to move to and attack, the golem attacks an object, with preference for an object smaller than itself. Once the golem goes berserk, it continues to do so until it is destroyed or regains all its hit points.

The golem's creator, if within 60 feet of the berserk golem, can try to calm it by speaking firmly and persuasively. The golem must be able to hear its creator, who must take an action to make a DC 15 Charisma (Persuasion) check. If the check succeeds, the golem ceases being berserk. If it takes damage while still at 40 hit points or fewer, the golem might go berserk again.

Aversion of Fire. If the golem takes fire damage, it has disadvantage on attack rolls and ability checks until the end of its next turn.

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

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

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

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

Detect Sentience. The golem can sense the presence and location of any creature within 300 feet of it that has an Intelligence of 3 or higher, regardless of interposing barriers, unless the creature is protected by a mind blank spell.

Telepathic Shroud. The golem is immune to any effect that would sense its emotions or read its thoughts, as well as to all divination spells.

Multiattack. The golem makes two Flensing Claws attacks and two Tentacle attacks. If the golem has a creature grappled, it can replace its tentacle attacks with its tentacle slam attack up to the number of creatures grappled.

Flensing Claws. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) slashing damage.

Tentacle. Melee Weapon Attack: +9 to hit, reach 10 ft., one creature. Hit: 19 (4d6 + 5) psychic damage, and the target is grappled (escape DC 14). Until this grapple ends, the golem can’t use this tentacle against other targets. The golem has two tentacles, each of which can grapple one creature.

Tentacle Slam. The golem slams creatures grappled by it into each other or a solid surface. Each creature must succeed on a DC 14 Constitution saving throw or take 12 (2d6 + 5) bludgeoning damage and be stunned until the end of the golem's next turn. On a successful save, the target takes half the bludgeoning damage and isn't stunned.