Embody Energy( Exemplars of Evil, p. 24)
You can sacrifice prepared spells to shroud your body in a particular type of energy.
You can sacrifice a spell that has an energy descriptor that matches the energy type you selected for Energy Substitution. By doing so, you wreathe your body with the energy for 1 round per level of the spell sacrificed. You are immune to the energy generated, and your natural attacks and attacks made with weapons deal an extra 1d6 points of damage of the appropriate type. Creatures that attempt to grapple you or that successfully attack you with a natural weapon or an unarmed strike take 1d6 points of damage for each hit or round of sustained contact.
You can select this feat multiple times. Each time, it applies to a new type of energy that you have selected for the Energy Substitution feat.