Chaos Beast (CR 7)

Medium Outsider (Chaotic and Extraplanar)
Alignment: Always chaotic neutral
Initiative: +5 (+1 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +11, and Spot +11

AC: 16 (+1 Dex, +5 natural), touch 11, flat-footed 15
Hit Dice: 8d8+8 (44 hp)
Fort +7, Ref +7, Will +6
Speed: 20 ft.
Space: 5 ft./5 ft.
Base Attack +8; Grapple +10
Attack: claw +10 melee
Full Attack: 2 claws +10 melee
Damage: Claw 1d3+2 and corporeal instability
Special Attacks/Actions: Corporeal instability
Abilities: Str 14, Dex 13, Con 13, Int 10, Wis 10, Cha 10
Special Qualities: immunity to critical hits and transformation, SR 15
Feats: Dodge; Improved Initiative; Mobility
Skills: Climb +13, Escape Artist +12, Hide +12, Jump +9, Listen +11, Search +11, Spot +11, Survival +0 (+2 following tracks), Tumble +14, and Use Rope +1 (+3 with bindings)
Advancement: 9-12 HD (Medium-size); 13-24 HD (Large)
Climate/Terrain: Ever-Changing Chaos of Limbo
Organization: Solitary
Treasure: None

Source: Monster Manual

Corporeal Instability (Su): A blow from a chaos beast can cause a terrible transformation. A living creature must succeed at a Fortitude save (DC 15) or become a spongy, amorphous mass. 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, unable to distinguish friend from foe (-4 penalty to hit and a 50% miss chance, regardless of the attack roll).

Each round the creature spends in an amorphous state deals 1 point of permanent Wisdom drain from mental shock. If the creature's Wisdom score falls to 0, it becomes a chaos beast itself.

A creature with a strong sense of self can regain its own shape by taking a standard action to attempt a Charisma check (DC 15), A success reestablishes the creature's normal form for 1 minute. On a failure, the creature can still repeat the check each round until successful.

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 restoration, heal, or greater restoration spell removes the affliction (a separate restoration is necessary to restore any lost Wisdom).

Immune to Transformation (Ex): No mortal magic can affect or fix a chaos beast's form. Effects such as polymorph or petrification force the creature into a new shape for a moment, but it immediately returns to its mutable form as a free action.

Chaotic Subtype

A subtype usually applied only to outsiders native to the chaotic-aligned Outer Planes. Most creatures that have this subtype also have chaotic alignments; however, if their alignments change they still retain the subtype. Any effect that depends on alignment affects a creature with this subtype as if the creature has a chaotic alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment. A creature with the chaotic subtype overcomes damage reduction as if its natural weapons and any weapons it wields were chaotic-aligned (see Damage Reduction).

Extraplanar Subtype

A subtype applied to any creature when it is on a plane other than its native plane. A creature that travels the planes can gain or lose this subtype as it goes from plane to plane. This book assumes that encounters with creatures take place on the Material Plane, and every creature whose native plane is not the Material Plane has the extraplanar subtype (but would not have when on its home plane). An extraplanar creatures usually has a home plane mentioned in its description. These home planes are taken from the Great Wheel cosmology of the D&D game (see Chapter 5 of the Dungeon Master's Guide). If your campaign uses a different cosmology, you will need to assign different home planes to extraplanar creatures.

Creatures not labeled as extraplanar are natives of the Material Plane, and they gain the extraplanar subtype if they leave the Material Plane. No creature has the extraplanar subtype when it is on a transitive plane; the transitive planes in the D&D cosmology are the Astral Plane, the Ethereal Plane, and the Plane of Shadow.