Pyroclastic Surge

8th-level evocation   Casting time: 1 action   Range: Self (60-foot cone)   Target: Each creature in the cone   Components: V S   Duration: Concentration, up to 1 minute   Classes: Sorcerer, Wizard, Warlock   Subclasses: --  
You summon a wave of flame, smoke and lightning that shoots forth from your outsstretchedhands. Each creature in the cone must make a Dexterity saving throw. A creature takes 6d6 fire damage and 6d6 lightning damage on a failed save, or half as much damage on a successful one. Every creature that fails the save is wreathed in embers and volcanic ash, which ignites them. Until a creature takes an action to douse the flames, the target takes 1d10 fire damage at the start of each of its turns.   The ash hangs in the air after casting, making the area count as heavily obscured as well as difficult terrain.