Hellfire Shield

Starting at 3rd level, you can call up hellfire to surround yourself with a protective barrier. Whenever someone directs a melee attack against you, you can, as an immediate action, aim a blast of hellfire at that creature. This blast deals damage equal to your eldritch blast (including bonus damage from the hellfire blast ability). This blast automatically strikes the target, which can attempt a Reflex saving throw for half damage (DC 10 + 1/2 your character level + your Cha modifier).

Each time you use this ability, you take 1 point of Constitution damage. Because the diabolical forces behind the power of hellfire demand part of your essence in exchange for this granted power, if you do not have a Constitution score or are somehow immune to Constitution damage, you cannot use this ability.