Disrupting Spell( Fiendish Codex II: Tyrants of the Nine Hells, p. 83)
You can cast spells that disrupt other caster's magical capabilities.
You can alter a spell so it interferes with one or more targets' supernatural and spell-like abilities, as well as any spells they cast. A disrupting spell temporarily reduces the save DC of any spell, spell-like, or supernatural ability the affected creature or creatures can cast or use by 2. The effect of a disrupting spell lasts for a number of rounds equal to the spell's unmodifi ed level. Multiple disrupting spells do not stack. A disrupting spell has no effect on magic items. A disrupting spell uses up a spell slot two levels higher than the spell's actual level.