3e SRD:Spell Focus
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Spell Focus [General]
Benefit: Choose a school of magic, such as Illusion. The character's spells of that school are more potent than normal. Add +2 to the Difficulty Class for all saving throws against spells from the school of magic the character selects to focus on.
Special: The character can gain this feat multiple times. Its effects do not stack. Each time the character takes the feat, it applies to a new school of magic.