Mordenkainen's Lost Notebook

Deadly Pahoehoe

8-level Evocation

You cause a torrent of molten rock to burst in a 60-foot cone from a point between your feet. Each creature in the cone must make a Dexterity saving throw. A creature takes 10d6 fire damage on a failed save, or half as much damage on a successful one. In addition, creatures which fail the save are coated in a thick layer of cooling magma, causing them to be petrified and take 5d6 additional fire damage at the start of their next turn.   If the creature survives the damage, it can use its action to attempt a DC 25 Strength check to break out of the hardened stone. It can also be chipped out by dealing bludgeoning damage to the stone, which has AC 20 and 50hp. In this case, half the bludgeoning damage transfers to the trapped creature.