D20:Energy Substitution Feat

Any other metamagic feat, Knowledge (arcana) 5 ranks.

You choose one type of energy: acid, cold, electricity, fire, or sonic. When employing a spell with the acid, cold, electricity, fire, or sonic designator, you can modify the spell to use your chosen type of energy instead. The altered spell uses a spell slot of the spell?s normal level.
The altered spell works normally in all respects except the type of damage dealt.

You can gain this feat multiple times. Each time the feat applies to a different type of energy.

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System Reference Document -> Feats