You look at an area within 500 feet of you and create a poisonous swamp. This swamp has a radius of 40 feet and counts as difficult terrain. When first cast, all creatures within this swamp must make a constitution save or take 10d6 poison damage and be poisoned. On a success, the creature takes half damage and is not poisoned. At the start of a creatures turn within the swamp, the creature must remake the constitution save or be affected by the swamp.