Rusalka
About
She is in the willows over the water in the week the rye is coming into ear, with her hair down and still wet, and she is laughing. Rusalki drowned, or were drowned, and did not get the rites. They do not fight and they do not strike. They call people into the water and hold them there while they tickle them, laughing the whole time, and this is genuinely how it is described and it is worse than a weapon would be.
Stats
Save Rolls
Traits
Special Attack
Come and Swim: 60 ft, save Wis Mind, fail save roll 2d6+3 psychic and the target walks into the water, cooldown 2 rounds. Hold and Laugh: against a creature in the water with her, no attack roll - she takes hold and does not let go. A held creature that cannot breathe water begins drowning and saves Con Tough each round. Breaking the grip needs a Strength Chance Roll against a TN the DN sets, or one turn from an ally in the water with them, which succeeds automatically. She never stops laughing while any of this is happening.
Special Defense
Of the Willow Week: she appears only in the weeks when the rye is greening and cannot be found at any other time of year. In the Water: she cannot be caught, held or struck while submerged, and she does not come out. Given the Rites: her name and her body are findable. Buried properly, with the words said, she is gone permanently and gratefully, and the water is safe from then on.