Your illusion spells are so realistic that creatures are inclined to believe them, even when faced with proof of their falsehood.

Prerequisites: Spell Focus (illusion)

Benefit: A character faced with proof that an illusion spell you cast isn't real must still make a saving throw, but does so at a +4 bonus. If any viewer successfully disbelieves an illusion you cast and communicates this fact to others, each such viewer gets a saving throw but gets no bonus to the check.

Normal: A character faced with proof that an illusion isn't real needs no saving throw. If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus.