Abysselle, Siren Queen

Many-Headed Horror.
Scylla has six serpentine heads sprouting from her body. She can take one additional bite attack as a bonus action on her turn.

Queen of the Jagged Rocks.
While within 30 feet of rocky terrain, shipwrecks, or cliffs, Scylla has advantage on Dexterity (Stealth) checks and opportunity attacks against creatures that move through her reach.

Siren’s Song (Recharge 5–6).
As a bonus action, Scylla sings a haunting melody. Each creature of her choice within 60 feet that can hear her must succeed on a DC 16 Wisdom saving throw or be charmed for 1 minute.

• While charmed, a creature is incapacitated and uses its movement to move toward Scylla by the safest route possible.

• The effect ends early if the creature takes damage or if another creature uses an action to shake it free.

Multiattack.
Scylla makes three Slam attacks or 3 Bite attacks. (or some mix)

Slam.
Melee Weapon Attack: +9 to hit, reach 15 ft., one target.
Hit: 13 (2d6 + 6) Blugeding damage.

Bite.
Melee Weapon Attack: +9 to hit, reach 10 ft., one target.
Hit: 14 (2d8 + 5) piercing damage.

Devour Sailor (Recharge 6).
Scylla targets one grappled, restrained, or charmed creature within 10 feet.
The target must make a DC 17 Constitution saving throw or take 36 (8d8) piercing damage and be restrained inside one of Scylla’s maws. A restrained creature can repeat the save at the end of each of its turns, escaping on a success.

Keening Stormsong. Ranged Spell Attack: +8 to hit, range 90 ft., one creature that can hear Scylla.
Hit: 22 (4d10) thunder damage, and the target must succeed on a DC 16 Wisdom saving throw or be Frightened of Scylla until the end of its next turn.

If the target is already charmed, it instead takes 33 (6d10) thunder damage and is knocked prone as the sound tears through wind and wave.

Storm Conductor. While a storm is raging, Keening Stormsong has advantage on its attack roll, and the thunder damage ignores resistance.

Bite.
Melee Weapon Attack: +9 to hit, reach 10 ft., one target.
Hit: 14 (2d8 + 5) piercing damage.

Snapping Heads.
When a creature within 10 feet misses Scylla with a melee attack, she makes one Bite attack against that creature.

Siren’s Song (Recharge 5–6 (turns)).
As a bonus action, Scylla sings a haunting melody. Each creature of her choice within 60 feet that can hear her must succeed on a DC 16 Wisdom saving throw or be charmed for 1 minute.

• While charmed, a creature is incapacitated and uses its movement to move toward Scylla by the safest route possible.

• The effect ends early if the creature takes damage or if another creature uses an action to shake it free.