Wall of Rot

You create a wall of poisonous spores and plants on a solid surface within range. You can make the wall up to 40 feet long, 10 feet high, and 1 foot thick, or a ringed wall up to 20 feet in diameter, 10 feet high, and 1 foot thick. The wall is opaque and lasts for the duration.

When the wall appears, each creature within its area must make a Constitution saving throw. On a failed save, a creature takes 5d6 poison damage and it is also poisoned until the end of its next turn, or half as much damage and is not poisoned on a success. 

The wall deals 5d6 poison damage to each creature that ends its turn within 5 feet or inside the wall. A creature takes the same damage when it enters the wall for the first time on a turn or ends its turn there.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for each slot level above 4th.