Chimeric Golem

Berserk. Whenever the golem starts its turn with 80 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 18 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.

Mutative Form. When the golem is targeted by any spell or effect that would alter its form, negate the effect and the golem can change one of its attack options to another unchosen option.

Chaotic Absorption. at the beginning of each round role a d10, whenever the golem is subjected to the damage that corresponds with the number rolled, it takes no damage and instead regains a number of hit points equal to the damage dealt.

1. acid 
2. cold
3. fire
4. force
5. thunder
6. lightning
7. poison
8. necrotic
9. psychic
10. radiant

Regeneration. The golem regains 15 health at the start of each of its turns.

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

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

Multiattack. The golem makes three attacks, one with each chosen attack.

Choose three, you cannot change these attacks until the creature dies or is targeted by a spell that alters its form:

Slam. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 27 (4d8 + 9) bludgeoning damage and must make a DC 20 strength saving throw or be nocked prone.

Claws. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Crit: 19-20 Hit:  27(4d8 + 9) slashing damage.

Bite. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 31(4d10 + 9) piercing damage and if the creature is medium or smaller it must succeed on a DC 18 dexterity saving throw or be swallowed, a swallowed creature is blinded and restrained, has total cover, and takes 27(6d8) necrotic damage at the start of each of its turns, it the golem takes more than 40 damage in a single turn from a creature inside it it must succeed on a DC 20 constitution saving throw at the end of that turn or regurgitate all swallowed creatures which fall prone within 10 feet of the golem. If the golem dies a swallowed creature is no longer restrained by it and can use 10 feet of movement to escape from the corpse, exiting prone.

Dragon Breath. Saving Throw: 40 ft cone., DC 20 DEX save. fail: 38(8d6) fire, cold, lightning, poison, or acid damage or half as much on a success.

Stinger. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 23(4d6 + 9) piercing damage and must make a DC 20 constitution save or take 39(6d12) poison damage and be paralyzed or half as much on a successful save and not be paralyzed.

Pincher. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 27(4d8 + 9) bludgeoning damage and be grappled.