Wave of Fire

You create a wall of fire on a solid surface within range. You can make the wall up to 40 feet long and 20 feet high. The wall travels 10 feet in a straight line every round, losing 2 feet of its height every 10 feet it moves, up to a maximum distance of 100 feet. 

When the wall appears or moves, each creature within its area of travel must make a Dexterity saving throw. On a failed save, a creature takes 5d8 fire damage, or half as much damage on a successful save. Creatures ending their turn within the wall take 5d8 fire damage. 

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 6th.