Your illusion spells are extremely potent when cast trickily.
Benefit: When you cast an illusion spell using the tricky spell class feature, you may either increase your caster level for that spell by a number of levels equal to your Charisma modifier or increase the Difficulty Class of the Will saving throw to resist the spell by the same amount. If the spell has the shadow descriptor and only has a partial effect if disbelieved (e.g. shadow evocation), the spell is considered 20% more real.
Undefeatable: The Collected Feats Sourcebook, Copyright 2009 – 2010, Louis Porter Jr. Design, Inc. Undefeated, Copyright 2011, Louis Porter Jr. Design, Inc.