Unraveler

This 10-foot-tall, vaguely humanoid form shimmers on the edge of existence. Though immaterial, its body seems to flash betwen phantom compositions of earth, air, fire, and water. 

Source: Planewalkers Handbook 3.5. Originally from the Planescape Monstrous Appendix III. It was called the Menglis in that book.

The Unraveler is born of oppositions. This elemental spirits is composed of earth, wind, fire, and water. The Unraveler sole existence is to break down the elements. These lawful neutral entities are known to reside on the borders of the Inner Planes. Where multiple elements mingle together. The signature ability of the Unraveler is to separate the elements that make up a body or object. Once a victim is afflicted by this ability it requires a charisma check to keep oneself composed. The ultimate monsters against players characters who dump their charisma attributes.

Combat: The Unraveler is a CR 9 Outsider.

-Disjoin: A blow from the Unraveler can cause a target to begin to seperate into component elements. The target must make a Fortitude Save or immediately take 2d8 points of damage. Within 2d4 rounds the target begins to unravel into a few pounds of minerals and a pool of liquid. Once affected by the disjoin ability the target can't cast spells, manifest psionics, or use magic items. He also attacks blindly unable to distinguish friends from foes. Attack rolls are made at -4 with a 50% miss chance.
   
     Each round that passes the target takes 2d8 points of damage as he rapidly decomposes. A victim can attempt to control his fading form by making a DC 15 Charisma check. Once made it suppresses the unraveling for 24 hours. Attempts can be made each round until the target succeeds or dies. The only way to cure the condition is through a restoration, heal, or greater restoration.

-Elemental Immunity: The Unraveler is immune to all types of elemental damage.

-Special Qualities: Spell Resistance 17 and darkvision 60ft. Also a large Outsider and it's claw attacks hit on a touch armor class.