Corruption (COFSA)

Slow and insidious, yet deadly nevertheless.
Your inflict a withering curse upon a 5-foot square of ground at a location you can see within range, withering plants and darkening the earth with fell power. At the start of each of your turns for the duration, the corruptive curse grows 5 feet in every direction. Whenever a creature starts its turn in a space afflicted by the curse, it must make a Charisma saving throw. If it fails, it takes 1d6 necrotic damage.

At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, the necrotic damage increases by 1d6 per spell slot level above 1st.