Consecrate Spell( Complete Divine, p. 79)
You can imbue your spells with the raw energy of good.
Any good alignment,
A spell you modify with this feat gains the good descriptor. Furthermore, if the spell deals damage, half of the damage (rounded down) results directly from divine power and is therefore not subject to be reduced by resistance or immunity to energy-based attacks. For example, a consecratedfirestorm spell cast by a 16th-level cleric deals 16d6 points of damage, half of which isfiredamage and half of which is sheer divine power. Thus, creatures immune tofirestill take damage. The consecrated spell uses up a spell slot one level higher than the spell's actual level.