Unstable Form. The Chaos Beast is immune to any spell or effect that would alter its form and it is immune to critical hits.
Corporeal Instability. A blow from a chaos beast can cause a terrible transformation. A living creature must make a DC 15 Constitution saving throw, becoming a spongy, amorphous mass on a failed save. Unless controlled through an act of will, the victim's shape melts, flows, writhes, and boils.
The affected creature is unable to hold or use any item. Clothing, armor, rings, helmets, and backpacks become useless. Large items - armor, backpacks, even shirts - hamper more than help, reducing the creature's Dexterity score by 4. Soft or misshapen feet and legs reduce speed to 10 feet or one-quarter normal, whichever is less. Searing pain courses along the nerves so strong that the creature cannot act coherently. It cannot cast spells or use magic items, and it attacks blindly with disadvantage, unable to distinguish friend from foe.
Each round the creature spends in an amorphous state reduces its Wisdom score by 1. If the creature's Wisdom score falls to 0, it becomes a chaos beast under the DM’s control.
A creature with a strong sense of self can regain its own shape by using their action to attempt a DC 15 Charisma check. A success reestablishes the creature's normal form for 1 minute.
Corporeal instability is not a disease or a curse and so is hard to remove. A shapechange or stoneskin spell does not cure the afflicted creature but fixes its form for the duration of the spell. A lesser restoration, heal, or greater restoration spell removes the affliction and restores all lost wisdom.
Multiattack. The chaos beast makes two claw attacks.
Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) slashing damage and effects of corporeal instability.