Wall of Ash

You create a wall of ash that blocks sight, 5ft thick, 15ft wide, and 10ft tall. This counts as rough terrain and a creature that moves through, starts it's turn inside of or moves into the wall must make a Constitution save DC 20 or take 24 (4d12) fire damage. A Creature that fails the safe is blinded for 1 round. Creatures that pass the save take half damage and are not blinded.

The wall can be curved and shaped in any way desired, after the spell ends, a pile of warm ashes lays on the round in it's space. Cold magic can destroy parts of the wall if it deals more then 30 points of cold damage. 

At higher levels the damage increases by 1d12 and the size increases by 10ft wider and 5ft taller.