Fihyr, Great (CR 15)

Medium Aberration
Alignment: Always chaotic evil
Initiative: +6 (Dex); Senses: darkvision 60 ft. and Spot +12

AC: 18 (+2 Dex, +6 natural), touch 12, flat-footed 16
Hit Dice: 16d8+16 (88 hp)
Fort +8, Ref +9, Will +14
Speed: 30 ft., fly 50 ft. (good)
Space: 10 ft./5 ft.
Base Attack +12; Grapple +12
Attack: 4 bites +12 melee
Full Attack: 4 bites +12 melee
Damage: Bite 2d6
Special Attacks/Actions: Emotion control, frightful presence
Abilities: Str 11, Dex 14, Con 12, Int 14, Wis 15, Cha 15
Special Qualities: invisibility, SR 18
Feats: Dodge; Great Fortitude; Improved Initiative; Iron Will; Lightning Reflexes; Mobility
Skills: Hide +21, Move Silently +21, Open Lock +21, and Spot +12
Advancement: 17-24 HD (Medium-size); 25-48 HD (Large)
Climate/Terrain: Any
Organization: Solitary
Treasure/Possessions: None

Source: Monster Manual II

Frightful Presence (Ex): Any creature that witnesses a great fihyr attacking becomes panicked if it fails a Will save (DC 20).

Emotion Control (Sp): At will, the great fihyr can produce an effect like that of an emotion spell (despair, fear, or hate only; caster level 16th; Will save DC 16), except that its range is 260 feet, its radius is 15 feet, and it lasts as long as the creature concentrates on it. The great fihyr can use this ability and remain invisible.

Invisibility (Ex): A great fihyr can become invisible at will. This effect is like that of the invisibility spell, except that the creature can remain invisible as long as it wishes, even while using its emotion control ability. Normally, a great fihyr is visible only immediately after delivering a melee attack.

Fihyrs attack by biting. The real purpose of fihyr's bite is not to deal damage, but to spread fear in others.

Great fihyrs begin any conflict by using their emotion control ability to generate negative emotions on which they can feed. Once they decide to become visible, they immediately attack so as to use their frightful presence ability.

Great fihyrs are unaffected by sunlight, but they despise it. Thus, they prefer to lay low during the day in dark, secluded spots, such as caves, dungeons, abandoned buildings, and the like.