Rokurokubi

She does not know. That is the part people find hard. By day she is an ordinary woman with an ordinary household and by night her neck extends across the room, along the corridor, up the stairs, and does things she wakes with no memory of. The body stays where it was put. Move the body while the head is away and she cannot find her way back to it, and the panic that follows is the most dangerous thing about her.

Reaching Neck: piercing, melee 30 ft, +4 to hit, 2d6+3, delivered from around a corner, through a doorway or over a screen while the body remains where it lies. Startle: 20 ft, save Wis Mind, fail save roll 2d6+2 psychic on any creature that sees the neck for the first time, cooldown 2 rounds.

The Body Sleeps: her body lies elsewhere, unconscious and undefended, and damage dealt to it is dealt to her. Anyone who follows the neck back finds it. Moved: if the body is moved more than a few paces while she is extended, she panics, breaks off entirely and spends the rest of the night looking for it. Wakes Innocent: at dawn she is herself, remembers nothing, and will help the party investigate the attacks with complete sincerity.