Mordha’s Explosive Shield

4th Level Evocation

Casting Time: 1 reaction, which you take when you are hit by an attack or targeted by the magic missile spell.
Range: 150 feet
Components: V S
Duration: 1 round.
Classes:  Arcane Trickster, Armorer, Artillerist, Battle smith, Cleric: Light Domain, Eldritch Knight, Monk, Sorcerer, Warlock: Fiend, Wizard

An invisible barrier of magical force appears and protects you. Until the start of your next turn, you have a +5 bonus to AC, including against the triggering attack, and you take no damage from magic missile. You then point your finger, and the creature that damaged you is momentarily surrounded by hellish flames. Each creature in a 20-foot-radius sphere centered on that creature must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one. The fire spreads around corners. It ignites flammable objects in the area that aren’t being worn or carried.

At Higher Levels: When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for each slot level above 4th.