Corrosive Array [two-actions] Feat 12

You command your nanites to sweep across the battlefield, damaging your enemies. You extend the duration of the cloud created by your Cloud Array until the end of your next turn, then you can move each square of the cloud up to 10 feet. The squares must each be contiguous to at least one other square of the cloud when the movement is complete. Until the start of your next turn, enemies that start their turn in the cloud take 3d6 acid damage with a basic Fortitude save against the higher of your class DC or spell DC. At 16th level and every four levels thereafter, increase the acid damage by 1d6.