Curtain of Fire

You bring into existence a curtain of flickering purple and pink flames that burns the life out of everything it touches. The curtain is 1 inch thick, up to 20 feet high, and up to 400 feet long. It is roughly straight; it can’t be curved or folded. You must be able to see the entire curtain when the spell is cast.

The curtain moves in a direction of your choice at a rate of 5 feet per round, consuming all organic matter in its path. Once a direction is chosen, the curtain moves that direction for the spell’s duration. If the spell is maintained for its full duration, the curtain will advance 500 feet and leave a scorched area 500 feet long by 400 feet wide. 

The flames generate no heat, but all organic material coming into contact with the curtain is treated as if struck by the disintegrate spell, but the damage type is fire rather than force. Buildings and items made from stone or metal are unharmed, but the magical fire can pass through up to 2 feet of stone or 2 inches of any metal and continue advancing. The magical fire burns life out of the soil as well, extending its horrid power to a depth of 5 feet beneath the surface of the earth.

Areas struck by a curtain of fire are easy to identify, as they are nothing but burned-out scars of black dust and sand unable to support any life.