Your training makes it difficult for enemy spellcasters to safely cast spells near you.

Prerequisites: 6th-level Fighter.

Benefit: The DC to cast spells defensively increases by +4 for all enemies that are within your threatened area. This increase to Casting Spells defensively only applies if you are aware of the enemy's location and are capable of taking an attack of opportunity. If you can only take one attack of opportunity per round and have already used that attack, this increase does not apply.