Julajimus (CR 12)

Huge Aberration
Alignment: Always neutral evil
Initiative: +6 (+2 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +10, and Spot +10

AC: 22 (-2 size, +2 Dex, +12 natural), touch 10, flat-footed 20
Hit Dice: 16d8+80 (152 hp); DR: 10/magic
Fort +10, Ref +7, Will +10
Speed: 50 ft.
Space: 15 ft./10 ft.
Base Attack +12; Grapple +29
Attack: Bite +19 melee and 2 claws +14 melee
Full Attack: Bite +19 melee and 2 claws +14 melee
Damage: Bite 3d10+9, claw 3d8+4
Special Attacks/Actions: Fear aura, roar, stunning
Abilities: Str 28, Dex 15, Con 20, Int 12, Wis 11, Cha 15
Special Qualities: enchantment immunity, polymorph self, fire resistance 10, sunlight vulnerability
Feats: Cleave; Great Cleave; Improved Bull Rush; Improved Initiative; Power Attack; Skill Focus (Disguise)
Skills: Climb +18, Disguise +14, Intimidate +12, Jump +18, Listen +10, and Spot +10
Advancement: 17-32 HD (Gargantuan); 33-48 HD (Colossal)
Climate/Terrain: Temperate forests
Organization: Solitary
Treasure/Possessions: Double standard

Source: Monster Manual II

Fear Aura (Su): A julajimus radiates a fear aura that can chill the blood of the bravest warrior. Any living creature within 20 feet of the monster must make a Will save (DC 20) or become frightened. Anyone who saves successfully is immune to this ability for 24 hours. Each round, a frightened subject gets a new saving throw at the same DC. This a mind-affecting fear effect.

Roar (Su): Three times per day a julajimus can loose an ear splitting roar that can be heard for miles. Every creature with 60 feet must make a Fortitude save (DC 23) or become deafened for 3d6 hours and take 6d6 points of subdual damage.

Stunning (Su): If a julajimus successfully scores a critical hit with its claws, the opponent must make a Fortitude save (DC 23) or be stunned for 1d4 rounds by the force of the blow. A stunned creature is unable to act and loses any positive Dexterity bonus to AC. Furthermore, any attacker gains a +2 bonus on attack rolls against it.

Enchantment Immunity (Ex): A julajimus is immune to all spells of the Enchantment school.

Alternate Form (Su): A julajimus can assume the form of any Tiny animal (typically a harmless, cuddly animal). Reverting to its true form is a free action. This ability helps the julajimus lull its victim into a false sense of security before it shifts into its natural form to attack.

Sunlight Vulnerability (Ex): A julajimus becomes paralyzed when exposed to sunlight. Each round, it can make a Fortitude save (DC 20) to resist the paralysis. Once paralyzed, it is helpless, although its damage reduction and fire resistance still make it difficult to kill. The paralysis lasts for 1d4 rounds after the exposure to sunlight ends.

Skills: A julajimus receives a +10 on Disguise checks when using its Alternate Form ability.

The julajimus enjoys the sensation of gnawing on living creatures, so it always attacks with its bite first, then follows up with slashes from its two claws. Despite its size, the julajimus is fast and can easily outrun most prey.