XIXECAL

Colossal Outsider (Chaotic, Cold, Evil, Extraplanar)
Hit Dice:  72d8+1,080 (1,676 hp)
Initiative:  +11 (+7 Dex. +4 Improved Initiative)
Speed:  140 ft.
AC:  58 (-8 size, +1 Dex, +55 natural)
Base Attack/Grapple:  +72/+116
Attack:  Claw +95 (2d8+28/19-20) melee
Full Attack:  2 claws +95 (2d8+28/19-20) melee, bite +89 (4d6+14) melee, stamp +89 (4d6+14) melee
Space/Reach:  50 ft./50 ft.
Special Attacks:  Rend 4d8+42, cold, spell-like abilities, breath weapon, summon white dragon, Constitution drain
Special Qualities:  Abomination traits, cold immunity, fire vulnerability, dire winter, fast healing 30, regeneration 30, SR 48, DR 20/good and epic and adamantine
Saves:  Fort +55, Ref +47, Will +39
Abilities:  Str 66, Dex 13, Con 40, Int 12, Wis 8, Cha 34
Skills: Climb +103, Concentration +90, Hide -9, Jump +28, Knowledge (arcana, religion, the planes) +76, Listen +70, Search +76, Spellcraft +76, Spot +76
Feats: Alertness, Cleave, Dodge, Great Cleave, Great Fortitude, Improved Critical (claw), Improved Initiative, Improved Sunder, Iron Will, Lightning Reflexes, Power Attack, Weapon Focus (bite), Weapon Focus (claw), Weapon Focus (stomp)
Epic Feats: Blinding Speed (x4), Devastating Critical (claw), Epic Toughness, Epic Weapon Focus (bite), Epic Weapon Focus (claw), Epic Weapon Focus (stomp), Overwhelming Critical (claw), Spell Stowaway (greater invisibility)
Climate/Terrain:  Any
Organization:  Solitary or in the company of 1d4+1 old white dragons
Challenge Rating:  36
Treasure:  Standard
Alignment:  Always chaotic evil
Advancement:  73-150 HD (Colossal)
A xixecal's natural weapons are treated as epic, evil, and chaotic-aligned for the purpose of overcoming damage reduction.

Combat

Rend (Ex): If the xixecal hits with both claw attacks, it latches onto the opponent's body and tears the flesh. This attack automatically deals an additional 4d8+42 points of damage.
Cold (Su): A hit from a xixecal's melee attack induces numbing cold. The opponent must succeed at a Fortitude save (DC 58) or be affected as though by a slow spell for 10 rounds. The DC is Charisma-based.
Spell-Like Abilities: At will-blasphemy, cone of cold, desecrate, greater dispel magic, dominate monster, hold person, greater invisibility, unholy aura, wall of ice; 5/day-haste, meteor swarm. Caster level 36th; save DC 22 + spell level. The DC is Charisma-based.
Breath Weapon (Su): Cone of cold, 300 feet, 3/day, damage 12d6, Fort half DC 61. The DC is Constitution-based.
Summon White Dragon (Sp): Five times per day a xixecal can summon an old white dragon.
Constitution Drain (Su): This effect permanently reduces a living opponent's Constitution score by 4 when the creature hits with a slam, bite, or rend, or twice that amount on a rend or critical hit. The creature heals 20 points of damage (or 40 on a rend or critical hit) whenever it drains Constitution, gaining any excess as temporary hit points. These temporary hit points last a maximum of 1 hour. The attack allows a Fortitude save (DC 58). The DC is Charisma-based.
Abomination Traits: Immune to polymorphing, petrification, and other form-altering attacks; not subject to energy drain, ability drain, ability damage, or death from massive damage; immune to mind-affecting effects; nondetection; true seeing at will; blindsight 500 ft.; telepathy out to 1,000 ft.
The standard fire resistance 20 most abominations have is not shared by xixecales
Dire Winter (Su): A xixecal always stands at the center of a permanent dire winter (epic spell)spell effect. If dispelled, the effect returns 1 minute later- the only way to permanently remove the effect is to slay the xixecal that generates it.
Regeneration(Ex): Xixecals take normal damage from Lawful weapons, and double damage from burning or fiery weapons.