Rain of Rust

You conjure a red raincloud in a 10-foot burst within 60 feet, which pours rust-colored rain directly below it. Any creature in the rain with the metal trait, that is made of metal, or is wearing metal armor is covered in corrosive build-up. Any such creature is Clumsy 1 as long as it remains in the area. If such a creature is in the rain at the start of its turn, it takes (((your level − 4) ÷ 2, rounded down) + 3)d6 damage with a basic Fortitude save against your class DC, plus 1d6 persistent damage if it fails. Damage from this impulse ignores Hardness. The cloud lasts 1 minute but ends if you use the impulse again.

Level (+2) The initial damage increases by 1d6.