Elemental Mastery

When you gain this feat, choose one of the following damage types: acid, cold, fire, lightning, or thunder.   You must have Elemental Adept in the damage type chosen.

Spells you cast ignore resistance and immunity to damage of the chosen type. In addition, you can change elemental (acid, cold, fire, lightning, or thunder) damage of spells to your chosen type.

You can select this feat multiple times. Each time you do so, you must choose a different damage type.