This creature's three singing heads sway atop serpentine necks that extend from a bulbous body split by a wide, toothy mouth.
Seaweed Siren CR 13
CN Large magical beast (aquatic)
Init +2; Senses darkvision 60 ft., low-light vision; Perception +17
Aura cacophony (100 ft., DC 22)
AC 26, touch 11, flat-footed 24 (+2 Dex, +15 natural, –1 size)
hp 184 (16d10+96)
Fort +16, Ref +12, Will +8
Immune mind-affecting effects; Resist fire 10, sonic 10
Speed 30 ft., swim 30 ft.
Melee bite +25 (4d6+15/19–20)
Ranged 3 sonic beams +17 (5d6 sonic)
Space 10 ft.; Reach 5 ft.
Special Attacks staggering gaze, trample (1d10+15, DC 28)
Spell-Like Abilities (CL 16th; concentration +19)
At will—shatter (DC 16)
1/day—bestow curse (DC 18, ranged touch attack, 30 ft.)
Str 30, Dex 15, Con 22, Int 11, Wis 16, Cha 19
Base Atk +16; CMB +27; CMD 39 (47 vs. trip)
Languages Aklo; tongues
SQ false heads, water dependency
Environment any coastlines
Cacophony (Su) A seaweed siren's noises disrupt spellcasting; casting within 100 feet of a seaweed siren requires a concentration check (DC 15 + the level of the spell being cast). All other concentration checks and Perception checks involving hearing made inside the aura have their DCs increased by 5. A siren can begin or end this ability as a free action. This is a sonic effect.
False Heads (Ex) A seaweed siren's false heads can be severed. To sever a head, an opponent must make a sunder attempt with a slashing weapon targeting the head. A head is considered a separate weapon with hardness 0 and hit points equal to the siren's Hit Dice (typically 16 hp). To sever a head, an opponent must deal enough damage to reduce the head's hit points to 0 or fewer. Severing a head deals an amount of damage to the siren's body equal to the siren's Hit Dice. A siren can't attack with a severed head. A siren with no remaining heads can't use its cacophony ability or its spell-like abilities.
Sonic Beams (Su) Each of the siren's false heads can fire a beam at a range of 60 feet, dealing 4d6 points of sonic damage.
Staggering Gaze (Su) Staggered 1d6 rounds, 30 feet, Will DC 22 negates. This is a mind-affecting effect. The save DC is Charisma-based.
Water Dependency (Ex) A seaweed siren can survive out of the water for 1 hour per point of Constitution (typically 22 rounds). Beyond this limit, a seaweed siren begins to suffocate.
A seaweed siren is a predator that uses false humanlike heads on its upper appendages in order to lure prey. The heads babble nonsense words and fragments of overheard sentences. If spoken to, they respond with words from a similar language. This behavior allows the seaweed siren to creep about under the water with only the heads showing, pretending to be swimming humanoids until it is ready to attack.