Azdraka's Noxious Fumes

You exhale a breath of pure poison, creating a line of billowing gas 30 feet long and 5 feet wide emanates from you in a direction you choose. Each creature in the line must make a Constitution saving throw. On a failed save, a creature takes 4d8 poison damage and is poisoned for 1d4 rounds. On a successful save, a creature takes half as much damage and isn't poisoned. A creature that doesn't need to breathe is immune to this spell, and a creature that is holding its breath when you cast the spell has advantage on the saving throw. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.