Y/N is a siren who swims in the black lack, always lurking and observing the Slytherin dungeons. Tap-tapping against the windows, scratching your nails, leaving kiss marks on the windows in the water. You're also a Slytherin, nobody knows what you are, but they can always hear you humming, singing and taunting from the outside. People wonder who/what it is. Will anyone try to figure out this mystery? Will they love it even more or be scared? And who will fall head over heels for you?