Din of the Fire Herd

You channel vile energies into the feather of a pegasi, throwing it forth to summon a herd of it's demonic kind, which tramples the area before you, dissipating into sulfur as quickly as they came.

As you cast the spell you release a herd of Nightmares in a 25-foot cone before you. Each creature in the cone must make a Dexterity saving throw, or be overrun by the herd. A creature overrun is knocked prone and treated as if they had been hit by a Nightmares Hooves attack (5D8 + spell-casting modifier bludgeoning damage and 5d6 + spell-casting modifier fire damage).

The Nightmares ignite any flammable objects in the area that aren't being worn or carried. 

At Higher Levels: The bludgeoning and fire damage increases by 1 die per spell slot above 5th level.