Cloak of cinders

You touch a willing creature who isn't wearing heavy armor, and a long flowing cloak of smoke, cinders, and ash surround the creature. 

the spell adds +2 to your Ac and when a creature makes a successful melee attack against you the cloak leaps out at them. The creature must make a Dexterity saving throw. It takes 2d10 fire damage on a failed save, or half as much damage on a successful one.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d10 for each slot level above 1st. and you gain and extra +1 to Ac for each slot level above 1st.