Profane Nimbus

You are surrounded by a nimbus of shadow. Any good creature striking you with unarmed strikes, natural weapons, or a handheld weapon deals normal damage, but at the same time, the attacker takes 1d6 points of damage + 1 point per caster level (maximum +15). Creatures wielding melee weapons with reach are not subject to this damage if they attack you. Spell resistance applies against this damage. You also take half damage from magical attacks with the good descriptor. If such an attack allows a saving throw for half damage, you take no damage on a successful saving throw.