Moonbeast (CR 16)

Huge Aberration
Alignment: Always chaotic evil
Initiative: +2 (Dex); Senses: all-around vision, darkvision 60 ft., Listen +11, and Spot +12

AC: 17 (-2 size, +2 Dex, +7 natural), touch 10, flat-footed 15
Hit Dice: 18d8+90 (171 hp)
Fort +11, Ref +8, Will +12
Speed: 30 ft., climb 10 ft.
Space: 15 ft./15 ft.
Base Attack +13; Grapple +17
Attack: 10 tentacle rakes +21 melee
Full Attack: 10 tentacle rakes +21 melee
Damage: Tentacle rake 4d6+10
Special Attacks/Actions: Bite 4d8+10, constrict 3d10+15, fear aura (DC 25), improved grab, spell-like abilities
Abilities: Str 30, Dex 15, Con 21, Int 8, Wis 9, Cha 18
Special Qualities: SR 22
Feats: Ability Focus (fear aura); Alertness; Cleave; Combat Reflexes; Great Cleave; Iron Will; Power Attack
Skills: Climb +22, Listen +11, Search +3, and Spot +12
Advancement: 19-27 HD (Huge); 28-36 HD (Gargantuan)
Climate/Terrain: Any land and underground
Organization: Solitary
Treasure/Possessions: 1/10th coins; 50% goods; 50% items plus 1 moonstone

Source: Monster Manual II

Bite (Ex): With a successful grapple check, a moonbeast can attempt to bite a grabbed opponent (+21 melee), dealing 4d8+5 points of slashing damage on a successful hit. A moonbeast cannot use its bite attack against a creature it has not already grabbed.

Constrict (Ex): With a successful grapple check, a moonbeast can crush a grabbed opponent, dealing 3d10+15 points of bludgeoning damage.

Fear Aura (Su): A moonbeast continually emanates a fear effect in a 60-foot-radius, centered on itself. Any creature within the area that fails a Will save (DC 23) is paralyzed with fear for 2d6 rounds. A new saving throw is required each time a potentially affected creature comes within range of the moonbeast.

Improved Grab (Ex): If a moonbeast hits an opponent that is at least one size category smaller than itself with a tentacle rake attack, it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity (grapple bonus +31). If it gets a hold, it automatically constricts and can attempt to bite the grabbed opponent in the same round. Thereafter, the moonbeast has the option to conduct the grapple normally, or simply use a single tentacle to hold the opponent (-20 penalty on grapple check, but the moonbeast is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals tentacle rake and constrict damage and allows another bite attempt.

Spell-Like Abilities: At will - dispel magic, fog cloud, improved invisibility, lightning bolt; 1/day - chain lightning, cloud kill, disintegrate, Evard's black tentacles, fireball, ice storm, mirror image, summon monster VI. Caster level 18th; save DC 14 + spell level.

All-Around Vision (Ex): A moonbeast can see in all directions at once. Because of this ability, it gains a +4 racial bonus on Search and Spot checks, and it cannot be flanked.

A moonbeast uses its improved invisibility ability to remain invisible even in combat. In battle, a moonbeast prefers to strike, grab, and constrict. It can use as many as seven of its tentacles against a single target.