Dark Aura (Invocation)

As an action, you summon an aura of dark energy to fortify you in combat.  Your AC becomes 10 + your Charisma modifier + your Dexterity Modifier while the Aura is active.  The aura extends 5 feet from you in every direction, but not through total cover. Any enemy that starts its turn in the aura takes necrotic damage equal to your Charisma modifier (minimum of 0 damage).  The Aura lasts until you're incapacitated or you dismiss it as a bonus action.