The material below is Open Game Content from a 3PP Source
This mermaid-like creature has the torso and head of a long-haired woman and the lower half of a sleek killer whale.
Cetaceal (CR 15; 51,200 XP)
NG Medium outsider (agathion, aquatic, extraplanar, good)
Init +8; Senses blindsense 60 ft., darkvision 60 ft., low-light vision; Perception +28
Aura protective aura (20 ft.)
AC 30, touch 15, flat-footed 25
(+4 Dex, +1 dodge, +15 natural; +4 deflection vs. evil)
hp 212 (17d10+119); regeneration 5 (evil weapons and spells)
Fort +17, Ref +16, Will +9; +4 vs. poison, +4 resistance vs. evil
DR 10/evil and silver; Immune cold, electricity, petrification; Resist sonic 10; SR 26
Speed 10 ft., swim 80 ft.
Melee +1 shocking burst shortspear +28/+23/+18/+13 (1d6+10 plus 1d6 electricity), tail slap +22 (1d6+4 plus push and stun)
Special Attacks shockwave, push (tail slap, 10 ft.)
Spell-Like Abilities (CL 15th; concentration +20)
Constant—speak with animals
At will—detect thoughts (DC 15), light, lightning bolt (DC 16), hold monster (DC 17), message, greater teleport (self plus 50 lbs. of objects only),
7/day—break enchantment, cure serious wounds, neutralize poison, remove disease
3/day—cone of cold (DC 18), cure critical wounds, greater restoration, heal
1/day—awaken, summon monster VIII (water elementals only)
Str 29, Dex 19, Con 24, Int 14, Wis 18, Cha 17
Base Atk +17; CMB +26; CMD 41 (can't be tripped)
Feats Combat Casting, Dodge, Improved Initiative, Lightning Reflexes, Mobility, Spell Penetration, Weapon Focus (shortspear, tail slap), Wind Stance
Skills Diplomacy +12, Handle Animal +14, Heal +21, Knowledge (arcana) +22, Knowledge (nature) +19, Knowledge (planes) +22, Perception +28, Sense Motive +24, Stealth +24, Swim +17; Racial Modifiers +4 Perception
Languages Celestial, Draconic, Infernal; speak with animals, truespeech
SQ amphibious, lay on hands (8d6, 11/day, as a 17th-level paladin)
Environment any water (Nirvana)
Organization solitary, pair, or pod (3–6)
Treasure double (+1 shocking burst shortspear, other treasure)
Protective Aura (Su) Against attacks made or effects created by evil creatures, this ability provides a +4 deflection bonus to AC and a +4 resistance bonus on saving throws to anyone within 20 feet of the cetaceal. Otherwise, it functions as a magic circle against evil effect and a lesser globe of invulnerability, both with a radius of 20 feet (caster level equals cetaceal's HD). The defensive benefits from the circle are not included in the above stat block.
Shockwave (Su) Once per day, a cetaceal can release a 100-foot-radius burst of energy. All creatures in the area take 17d6 damage; half of this damage is cold, and half is electricity (DC 25 Reflex save halves). The save DC is Constitution-based.
Stun (Ex) Any creature moved by a cetaceal's push attack must make a DC 25 Fortitude saving throw or be stunned for 1 round. The DC is Constitution-based.
Cetaceals are great water-dwelling agathions who swim the planar seas and commune with the creatures of the deeps. Rarely seen by landwalkers, they defend the waters against aquatic evils such as aboleths. Their spirits usually were those of great mortal leaders of aquatic or coastal tribes, or good folk who died underwater serving some great cause, reborn in a celestial form that is part humanoid, part orca. They are social beings and develop close friendships with other celestials and marine creatures.
A cetaceal is 8 feet long and weighs 400 pounds, although some grow quite a bit larger than that.