SRD:Empathic Feedback

You empathically share your pain and suffering with your attacker. Each time a creature strikes you in melee, it takes damage equal to the amount it dealt to you or 5 points, whichever is less. This damage is empathic in nature, so powers and abilities the attacker may have such as damage reduction and regeneration do not lessen or change this damage. The damage from empathic feedback has no type, so even if you took fire damage from a creature that has immunity to fire, empathic feedback will damage your attacker.

Augment: For every additional power point you spend, this power’s damage potential increases by 1 point.