Hellfire

Waves of white-hot fire engulf the area surrounding you as you cackle with fel power, horribly burning all creatures and unattended objects. As you concentrate, the fires continue to burn at the cost of your own life force. All other creatures within 15 feet of you must make a Dexterity saving throw or take 14d8 fire damage, or half as much damage on a successful one, and you take 2d6 fire damage that cannot be reduced by any means, but it does not provoke a concentration saving throws. Additionally, the fel magics that flow through you empower you, giving you advantage on concentration checks. On your turn, you can use your action to continue channeling hellfire, increasing the radius by 5 feet each time. If you move more than half your speed or use your action for anything besides channeling hellfire, the spell ends.

At Higher Levels. When you cast this spell using a spell slot of 9th level or higher, the fire damage increases by 4d6, but the damage you take increases by 1d6 for each slot level above 8th.