Arcane Consumption

(Player's Handbook II, page 74, DnD 3.5)

[General]

You can sacrifi ce your physical health to strengthen a spell. This process leaves you wracked with pain, but the enhanced energy you draw from the spell might provide the margin between victory and defeat.

Prerequisite

Arcane Toughness, Toughness, arcane caster level 6th

Benefit

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.