Aspect of Dragon Fire

Choose a target within range that you can see. The target must make a Dexterity saving throw, taking 5d10 fire damage on a failed save, or no damage on a successful one. If the target fails the saving throw, fire bursts out in a 15-foot cone extending from the point of impact in a direction of your choosing (not affecting the target). All creatures in the cone must make a Dexterity saving throw, taking 3d8 fire damage on a failure or half as much on a success.