Piercing Evocation

 
Prerequisite(s): Spell Focus (Evocation) or Evoker 1st level
 
Benefit: When you cast an evocation spell that deals energy damage (acid, cold, fire, electricity, or sonic), you can choose for 10 points of energy damage dealt by the spell to become untyped damage to which energy resistance and immunity do not apply. If the spell deals multiple types of energy damage, you choose how much of each type is converted by this feat after rolling damage.
 
Special: An evoker can select this feat as a wizard bonus feat.
 
Source: Complete Mage