Acidic Armor

You manifest a protective layer of acidic slime over your body as a reaction against danger. You gain 20 temporary hp until the end of the round, and any creature that successfully hits you with a melee attack automatically takes Acid damage equal to your Spell Attack Modifier. In addition, when the spell ends or the temp hp is depleted, you can choose to have the slime explode in a 10ft radius. Any creature in this radius must success on a Dexterity Saving Throw, taking 2d4 Acid damage on a fail, or none on a success.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the initial damage increases by 1d4, and the temporary hp increases by 10, for every two spell slot levels above 3rd.