Tyrewyrm Strike

You engulf your fists/weapon in flames and make a melee attack against one creature within 5 feet of you. On a hit, the target suffers the attack’s normal effects and takes 1d10 Fire Damage. Your strike causes a rupture of flame causing 1d10 damage to all within a 10 foot radius. 

At Higher Levels. At 5th level, the melee attack deals an extra 1d10 fire damage to the target on a hit, and the fire damage caused increases to 2d10. Both damage rolls increase by 1d10 at 11th level (3d10 and 3d10) and 17th level (4d10 and 4d10).