Iso-Onna are incredibly dangerous sea-vampires from Japanese folklore that manifest as beautiful women to entice victims before attacking them with their long hair, which is also used to drain their blood.
These spirits possessed an array of magical powers and could sing to lure victims off cliffs or shriek to stun people.
They could disguise themselves as rocks when they didn't wish to be seen and could grow to unimaginable size in order to crush entire ships if the mood pleased them.