Bonerattle

You target a creature that has a skeletal structure within range. That creature must make a Constitution saving throw at the start of each of their turns. On a failed save, the creature’s bones vibrate painfully and disturbingly, like a resin bow is being drawn across them. The creature takes 2d6 thunder damage and 2d6 necrotic damage at the start of each of their turns. The creature’s movement speed is halved. A successful save halves the damage and the creature can move normally during that turn, but does not end the spell.