Devouring Flame

Four bright serpents of reddish-yellow flame burst from your fingertips, darting to four points you choose within range and explode with a single loud blast into four incandescent conflagrations. Each creature in a 20-foot radius sphere centered on each point must make a Dexterity saving throw. A target takes 12d6 fire damage on a failed save, or half as much on a successful one. The fire spreads around corners. It ignites flammable objects in the area that aren't being worn or carried.

All targets, irrespective of the Dexterity saving throw, are set alight for the spell's duration or until a creature uses its action to extinguish the flames of itself or another creature. A burning creature takes 3d6 fire damage at the start of each of its turns.