Black Rose Thorns

Choose a point you can see within range, from Which a field of crimson roses sport within 50 feet of the chosen point, the field is considered difficult terrain. Every non undead inside  creature inside of the field must make a Constitution saving throw DC (14) at the start of their turn. The creature takes 2d4 necrotic damage on a failed save, or half as much on a successful one. Every creature that dies in the field will increase the damage by 2d4 to maximum of 20d4.