Verdigris March

Description

You touch a drop of vinegar to the ground and a slow tide of green corrosion begins to walk. A 60-foot line of creeping verdigris spreads out from you, 10 feet wide, advancing along whatever surface it can find: flagstones, hulls, siege engines, armor. Each creature in the line must make a Dexterity saving throw, taking 4d8 acid damage on a failed save, or half as much on a successful one. Metal objects in the line that are not being worn or carried are automatically covered in patina and become brittle. A creature wearing metal armor that fails its save takes a cumulative -1 penalty to AC as its plates corrode, to a minimum of the armor's base value without its metal reinforcement. At the start of each of your turns for the duration, the march advances another 10 feet in a direction you choose, and any creature it reaches must save again. The verdigris is inert to flesh, wood, and stone, which is why besieging armies love it and why the smiths who must scour it off afterward do not.