Chaos Elemental

 Chaos Element. Whenever the elemental deals force damage through its abilities, the force damage has a chance to be replaced with a random element, roll a d6 to determine the damage type:

1. force
2. cold
3. lightning
4. acid
5. poison
6. fire

Chaos Form. The elemental can move through a space as narrow as 1 inch wide without squeezing. A creature that touches the elemental or hits it with a melee attack while within 5 feet of it takes 5 (1d10) force damage. In addition, the elemental can enter a hostile creature's space and stop there. The first time it enters a creature's space on a turn, that creature takes 5 (1d10) force damage

Death Throes. When the elemental dies, it explodes, and each creature within 30 feet of it must make a DC 16 Dexterity saving throw, taking 44 (8d10) force damage on a failed save, or half as much damage on a successful one

Innate Spellcasting (Elemental form only). The elemental's innate spellcasting ability is Charisma (spell save DC 16, +8 to hit). The elemental can innately cast the following spells, requiring no material, somatic or verbal components.

At will: absorb elements, chaos bolt

1/day: freedom of movement

Shapechanger. The elemental can use its action to polymorph into any large or smaller corporeal creature or object, or back into its true elemental form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies or makes a Chaos Overload attack.

Multiattack (Corporeal Form Only). The elemental makes two swipe attacks and one pummel.

Swipe (Corporeal Form Only). Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.

Pummel (Corporeal Form Only). Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 18 (2d12 + 5) bludgeoning damage.

Chaos Overload (recharge 5-6). The elemental bursts chaotic energy into its surrounding area.  Each creature within 30 feet of the elemental must succeed on a DC 16 Dexterity save or take 22 (4d10) force damage.