Aura of Tsathogga

A swirling mist of corrosive green vapor engulfs your body for the duration of the spell. You gain resistance to acid damage.  Any creature that hits you with a melee attack takes 4d6 acid damage.  

Additionally, as an action, you can make a melee spell attack against one creature.  On a hit, the creature takes 10d6 acid damage and the spell ends.