Choose a school of magic, such as illusion. Your spells of that school are far more potent than normal.
Prerequisites: Greater Spell Focus in the selected school, ability to cast at least one 9th-level spell of the selected school.
Benefit: Add +1 to the DC of all saving throws against spells from the school of magic you select. This bonus stacks with the bonuses from Spell Focus and Greater Spell Focus.
Special: You can gain this feat multiple times but its effects do not stack. Each time you take the feat, it applies to a different school of magic.
Source: Complete Arcane, page 192.