Needs review
Source: Player's Handbook II

Description: +4 Spell DC, Take 4 CON Damage and fatigue yourself

Prerequisites: Toughness, Arcane Toughness, 6th level Caster

Once per day as a swift action, you can grant the next spell you cast a +4 bonus on its save DC. You must cast and complete this spell on the same turn that you use a swift action to activate this feat. In return, you take a -4 penalty to Constitution for 12 hours and are fatigued.