PFSRD:Greater Spell Focus
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Greater Spell Focus
Choose a school of magic to which you have already applied the Spell Focus feat. Any spells you cast of this school are very hard to resist.
Prerequisite: Spell Focus.
Benefit: Add +1 to the Difficulty Class for all saving throws against spells from the school of magic you select. This bonus stacks with the bonus from Spell Focus.
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 to which you already have applied the Spell Focus feat.