Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

Prerequisites

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

Benefit: 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.

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

High Arcana: Mastery of the Elements (requires 8 levels of Archmage)
Specifics: At the cost of one 8th level spell you gain the ability convert spells from one element into another. This ability can be used at will. If no sacrficed spell slot is available the ability cannot be used. Spell slots are sacrificed the first time the feat is used after resting and must contain a memorized spell. Note that this won't enable a Frostmage to use their piercing cold ability on spells that aren't cold-based to begin with.
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