Mirror Warrior (3.5e Invocation)
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This invocation functions as the arcane spell Mirror Image. Additionally, the images count as flankers for you, but this bonus is lost any time when the person being flanked knows which images is the real caster (such as by using other means of detection, successfully attacking them, or being attacked by them), unless the caster and images change their locations (e.g. by taking a five foot step).
Note: Since images must remain within five feet of the caster or another image, there must be at least three images to successfully flank an opponent.