Deadly Lahar

A rushing torrent of liquid rock bursts from the ground, washing over your foes.   You create a liquid landslide of molten-hot volcanic material.   All creatures in the area of the spell take 10d6 points of fire damage.   Additionally, those creatures are coated in a thick layer of the viscous substance, slowing them (as the slow spell) for the next 3 rounds and dealing an additional 5d6 points of fire damage per round.   A successful Reflex save reduces the initial damage by half and prevents the slow effect and the additional damage.
 

You cause a rushing torrent of liquid rock to burst from the ground in front of you, washing over your foes. Each creature in a 60-foot Cone must make a Dexterity saving throw, taking 10d6 fire damage and being slowed on a failure, or half damage and not slowed on a success. While slowed in this way, the creature is counted as being under the effects of the Slow spell, but needs a Strength saving throw to rip the solidifying rock off them rather than a Wisdom saving throw, ending the spell on themselves on a success. When a creature starts its turn slowed by this spell, it takes 5d6 fire damage.   At Higher Levels. When you cast this spell using a higher level spell slot, increase the range by 20 feet for each slot level above its base level.