Chaoswyrd (CR 12)

Huge Aberration
Alignment: Always chaotic neutral
Initiative: +2 (Dex); Senses: darkvision 120 ft., Listen +17, and Spot +14

AC: 20 (-2 size, -2 Dex, +14 natural), touch 6, flat-footed 20
Hit Dice: 18d8+72 (153 hp); DR: 10/lawful
Fort +10, Ref +4, Will +7
Speed: 30 ft.
Space: 20 ft./20 ft.
Base Attack +13; Grapple +29
Attack: Bite +19 melee
Full Attack: Bite +19 melee, 4 tentacles +14 melee
Damage: Bite 2d6+8, tentacle 2d8+4
Special Attacks/Actions: Improved grab, constrict (2d6+4), madness, spell-like abilities, parasites
Abilities: Str 27, Dex 6, Con 19, Int 22, Wis 3, Cha 12
Special Qualities: fast healing 10
Feats: Cleave; Combat Casting; Dodge; Great Cleave; Improved Bull Rush; Improved Critical (bite); Improved Initiative; Improved Sunder; Iron Will; Power Attack,
Skills: Concentration +25, Knowledge (arcana) +27, Knowledge (the planes) +27, Listen +17, Move Silently +17, Spellcraft +29, Spot +14, and Survival +17
Advancement: 19-26 HD (Huge), 27-54 HD (Gargantuan)
Climate/Terrain: Any land and underground
Organization: Solitary
Treasure/Possessions: Standard (no coins)

Source: Dragon #287
Dragon Compendium Vol. 1

Improved Grab (Ex): If the chaoswyrd hits a creature of up to Large size with a tentacle, it deals normal damage and can immediately attempt to start a grapple as a free action without provoking an attack of opportunity. If the chaoswyrd gets a hold of its target, it can constrict.

Constrict (Ex): After a successful grapple check, the chaoswyrd's tentacle automatically constricts the target for 2d6+4 points of damage per round until the hold is broken.

Madness (Su): Once per round as a free action, a chaoswyrd can mentally communicate with any one creature in line of sight. This communication fills the target's mind with chaos; the target must make a Will saving throw (DC 20) or suffer from a continuous confusion effect as per the insanity spell. Remove curse does not remove this supernatural effect. Greater restoration, limited wish, miracle, or wish can restore the creature.

Spell-Like Abilities (Sp): At will - chaos hammer, confusion, detect law, detect magic, detect thoughts, dimensional anchor; dispel law, hallucinatory terrain, magic circle against law, mirror image, protection from law, rainbow pattern, random action, see invisibility; 3/day - cloak of chaos, symbol of insanity, word of chaos. These abilities are as the spells cast by an 18th-level sorcerer (save DC 11 + spell level).

Parasites (Su): The swarming parasites that coat the lower regions of a chaoswyrd's body are highly magical and exist only partially in reality. They feed on the chaoswyrd's more logical thoughts, thoughts for which the chaoswyrd has little use. This feeding continues at all times and creates an aura of discordant mental fog to a radius of 30 feet from the chaoswyrd. Each round, all living creatures within this area must make a Will saving throw (DC 15) or suffer 1d4 points of temporary Wisdom damage as some of their thoughts are swept up and consumed by the parasites. Creatures with Wisdom scores of 3 or lower cannot be perceived by the parasites and are immune to their mind-draining frenzy.

A chaoswyrd's attacks reflect their insanity; they aren't known for complex tactics. One round, the creature might lash out with its tentacles and bite, the next round it might use a spell-like ability, and the round after that it might begin talking to its victims with idle interest. Some adventurers tell stories of how they were able to distract an attacking chaoswyrd by posing philosophical questions about the planes, causing the creature to forget about attacking to ponder the question. Successfully distracting a chaoswyrd in this manner requires an opposed Knowledge (the planes) skill check.