Your spells of that element are more potent than normal.
Benefit
Choose an element (earth, fire, ice, lightning, water, or wind). Add +1 to the Difficulty Class for all saving throws against spells from the element you select, but a -1 to that element’s weakness.
Special: You can gain this feat multiple times. Its effects do not stack. Each time you take this feat, it applies to a new element type. This feat does not stack with the Spell Focus feat.