Rusalka

A constant spell affects the monster without the monster needing to cast it, and its duration is unlimited. If a constant spell gets counteracted, the monster can reactivate it by spending the normal spellcasting actions the spell requires.

A rusalka is Concealed while underwater.

The rusalka cries out a compelling invitation. Each non-fey creature within a 300-foot emanation must attempt a DC 27 will save. The effect lasts for 1 round, but if the rusalka uses Beckoning Call again on subsequent rounds, the duration extends by 1 round for all affected creatures. Once a creature succeeds at any save against Beckoning Call, that creature is temporarily immune for 24 hours. Success The creature is unaffected. Failure The creature is Fascinated and must spend each of its actions to move closer to the rusalka, avoiding obvious dangers. If a beckoned creature is adjacent to the rusalka, it stays still and doesn't act. If attacked by the rusalka, the creature is freed from captivation at the end of the rusalka's turn. Critical Failure As failure, but if attacked by the rusalka, the creature can attempt a new save only at the start of its next turn, rather than being freed at the end of the rusalka's turn.

(2d8+10) bludgeoning, DC 32 fortitude The monster deals the listed amount of damage to any number of creatures Grabbed or Restrained by it. Each of those creatures can attempt a basic Fortitude save with the listed DC.

A rusalka can have up to eight creatures grabbed within their tresses at a time.

The rusalka attempts an athletics check against each Grabbed creature's Fortitude DC. The rusalka moves each creature they succeed against up to 10 feet and each creature they critically succeed against up to 20 feet. This movement must all be within reach of its tresses.

The rusalka touches a creature within 5 feet using their hand, stirring up memories of regret and shame. The target must attempt a DC 35 will save. Critical Success The target is unaffected. Success The target is Sickened 1. Failure The creature is sickened 1 and Stunned 1. Critical Failure The creature is sickened 1 and stunned 1, and it must use its first action on its next turn to Strike itself, automatically hitting.

Trigger The monster's last action was a successful Strike that lists Improved Grab in its damage entry, or the monster has a creature Grabbed or Restrained Effect If used after a Strike, the monster attempts to Grapple the creature using the body part it attacked with as a free action. This attempt neither applies nor counts toward the creature's multiple attack penalty. The monster can instead use Improved Grab as an action and choose one creature it's grabbing or restraining with an appendage that has Improved Grab to automatically extend that condition to the end of the monster's next turn.