Spellbane Level 6

Source SAP1

A weapon with the spellbane fusion gains the spellbane critical hit effect. A target affected by the spellbane critical hit effect must succeed at a Will save (DC as normal for a weapon of the given item level) or be unable to cast spells or use spell-like abilities for 1d4 rounds. If the weapon already has a critical hit effect, you can choose to apply either the weapon’s normal critical hit effect or the spellbane effect when you score a critical hit.

If a spellbane weapon also has a fusion that allows it to bypass damage reduction of a specific alignment (such as an unholy weapon’s ability to bypass DR/evil), its spellbane critical hit effect works only against creatures with the diametrically opposed alignment (for example, good creatures in the case of a spellbane unholy weapon), but the save DC of the spellbane critical hit effect increases by 2.