Spell Focus

The material below is Open Game Content from a 3PP Source

Spell Focus
Choose a school of magic. Any spells you cast of that school are more difficult to resist.
Benefit: Add +1 to the Difficulty Class for all saving throws against spells from the school of magic you select.
Special: You can gain this feat multiple times. Its effects do not stack. Each time you take the feat, it applies to a new school of magic.