Cloaker (CR 5)

Large Aberration
Alignment: Usually chaotic neutral
Initiative: +7 (+3 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +13, and Spot +13

AC: 19 (-1 size, +3 Dex, +7 natural), touch 12, flat-footed 16
Hit Dice: 6d8+18 (45 hp)
Fort +5, Ref +5, Will +7
Speed: 10 ft., fly 40 ft. (average)
Space: 10 ft./10 ft. (5 ft. with bite)
Base Attack +4; Grapple +13
Attack: Tail slap +8 melee
Full Attack: Tail slap +8 melee and bite +3 melee
Damage: Tail slap 1d6+5, bite 1d4+2
Special Attacks/Actions: Moan, engulf
Abilities: Str 21, Dex 16, Con 17, Int 14, Wis 15, Cha 15
Special Qualities: Shadow shift
Feats: Alertness; Combat Reflexes; Improved Initiative
Skills: Hide +8, Listen +13, Move Silently +12, and Spot +13
Advancement: 7-9 HD (Large); 10-18 HD (Huge)
Climate/Terrain: Underground
Organization: Solitary, mob (3-6), or flock (7-12)
Treasure/Possessions: Standard

Source: Monster Manual

Moan (Ex): A cloaker can emit a dangerous subsonic moan instead of biting. By changing the frequency, the cloaker may cause one of four effects. Cloakers are immune to these sonic, mind-affecting attacks. Unless noted otherwise, creatures who successfully save against these effects cannot be affected by the same moan effect from the same cloaker for one day.

Unnerve: All within an 80-foot spread automatically suffer a -2 morale penalty to attack and damage rolls. Those forced to hear the moan for more than 6 consecutive rounds must succeed at a Will save (DC 15) or enter a trance, unable to attack. or defend themselves until the moaning stops. Even on a success, they must repeat the save in each round the moaning continues.

Fear: All those within a 30-foot spread must succeed at a Will save (DC 15) or flee in terror for 2 rounds.

Nausea: Everyone in a 30-foot cone must succeed at a Fortitude save (DC 15) or be overcome by nausea and weakness. Affected characters fall to the ground and are unable to take any actions, including defending themselves for 1d4+1 rounds.

Stupor: A single creature within 30 feet of the cloaker must succeed at a Fortitude save (DC 15) or be affected as though by a hold person spell for 5 rounds. Even after a successful save, the creature must repeat the save if the cloaker uses this effect again.

Engulf (Ex): A cloaker can try to wrap a Medium-size or smaller creature in its body as a standard action. The cloaker attempts a grapple that does not provoke an attack of opportunity. If it gets a hold, it bites the engulfed victim with a +4 attack bonus. It can still use its whip like tail to strike at other targets.

Attacks that hit an engulfing cloaker deal half their damage to the monster and half to the trapped victim.

Shadow Shift (Su): Cloakers can manipulate shadows. This ability is effective only in shadowy areas and has several possible effects.

Obscure Vision: The cloaker gains one-quarter concealment (10% miss chance) for 1d4 rounds.

Dancing Images: This duplicates a mirror image spell cast by a 6th level sorcerer.

Silent Image: This duplicates a silent image spell cast by a 6th-level sorcerer.

Cloakers usually lie still, watching and listening for prey. If a single opponent, a cloaker uses its engulf attack. Against multiple foes, it lashes with its tail in concert with its moan and shadow shift abilities to reduce the opposition's numbers, then engulfs a survivor. Multiple cloakers usually split up, leaving one or two behind to use special abilities while the rest attack.