DreadPirateMurphy
Explorer
Rechan gave me an idea for a new type of adaptive camouflaging system not built on manipulation of environmental correspondence but built entirely on exploiting sensory misdirection (that is you would be able to see something is there but not process or understand what it is you were looking at, one thing would appear as another based upon human visual recognition patterns - the immediate effect would only last until the target thought carefully about what he is perceiving, but then again the effect could be both adaptive and cyclical).
As for gaming applications it seems to me that Rechan is really onto something about projecting "sensory confusion" against enemy types depending on their physiology and biology.
Wasn't this part of the premise of 3.x illusion magic? IIRC, an illusion was mind-affecting, i.e., all in the opponent's head. Turning invisible wouldn't make you literally invisible -- other folks just couldn't perceive that you were there. Invisibility sticks in my mind because of all of the angst caused by arguments over how it worked in previous editions.
Now, I could see changing perception in more subtle ways to create interesting effects. There are a number of mental disorders that are downright bizarre in real life. For example, prosopamnesia is a condition where the sufferer cannot remember faces. Everybody seems a stranger to them. How confusing would that be, especially if it was "sudden onset," i.e. magical? Capgras delusion is a disorder where a person believes that a close friend or relative has been replaced with an exact duplicate. In a fantasy world where doppelgangers actually exist, the sufferer might actually be able to convince others that their perception is true!
Real-world disorders would make good fantasy curses, especially plot-driven ones, I think...