Needs review
Source: Player's Handbook

Description: Your spells of your chosen school are now even more potent than before.

Prerequisites: Spell Focus

Required for: Epic Spell Focus

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 of magic to which you already have applied the Spell Focus feat.