Ancient Chaos Beast

Amorphous. The Ancient Chaos Beast can move through a space as narrow as 1 inch wide without squeezing.

Destabilize. A creature that touches the Ancient Chaos Beast or hits it with a melee attack while within 5 feet of it must make a DC 17 Constitution saving throw or be poisoned for 1 minute. A creature poisoned in this way takes 21 (6d6) necrotic damage at the start of each of its turns. It can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If the creature’s saving throw is successful or the effect ends for it, the creature is immune to the Ancient Chaos Beast’s Destabilize for the next 24 hours.

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

Amorphous Offense. At the start of each of the Ancient Chaos Beast's turns, roll 2d4 to determine the body parts at its disposal

1. Claw
2. Stinger
3. Tentacle
4. Spine Shot

Multiattack. The Ancient Chaos Beast makes two attacks with each of its body parts

Claw. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 17 (2d10 + 6) slashing damage plus 11 (3d6) necrotic damage. The creature must make a DC 17 Constitution saving throw or be affected by the Ancient Chaos beast’s Destabilize effect.

Stinger. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 12 (1d10 + 6) piercing damage plus 14 (4d6) necrotic damage  The creature is grappled until the start of The Ancient Chaos Beasts next turn. The creature must make a DC 17 Constitution saving throw or be affected by the Ancient Chaos beast’s Destabilize effect.

Tentacle. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 28 (4d10 + 6) bludgeoning damage. The creature must make a DC 18 Strength saving throw or be knocked prone. The creature must make a DC 17 Constitution saving throw or be affected by the Ancient Chaos beast’s Destabilize effect.

Spine Shot. Ranged Weapon Attack: +7 to hit, range 25/50 ft., one target. Hit: 37 (4d10 + 4) piercing damage plus 14 (4d6) necrotic damage.