Toxicity

A 15 ft radius sphere of poisonous gas appears centered on a point you can see within range. Every creature inside the area when it is cast or that enters the area must succeed on a constitution saving throw or the creature is poisoned for the duration of the spell. If a creature enters or starts its turn in the area while already poisoned, they make a constitution saving throw, taking 4d6 poison damage on a failed save or half damage on a passed save. Every time a creature fails this save on consecutive turns, increase the damage by 2d6.

At higher levels, increase the initial poison damage and the amount of damage the spell increases by, by 2d6 per level cast above 1st.