Retch Rust

You exhale tendrils formed from flakes of rusted metal. All creatures in a 30-foot cone take (((your level − 8) ÷ 2, rounded down) + 4)d10 slashing damage with a basic Fortitude save against your class DC. A metal creature that fails its save also takes (((your level − 8) ÷ 2, rounded down) + 2)d4 persistent slashing damage.

Level (+2) The cloud's slashing damage increases by 1d10 and the persistent damage increases by 1d4.