My apologies to anyone who saw this on Reddit.
I was thinking about an enhanced Wizard's Sidestep that not only moves the image, but moves the sound, so that it makes it harder to figure out where the Wizard is. The stats for WS are:
(Base 2, +2 Sun, +1 changing image, +1moved image matches changes)
Adding a sense adds +1.
And would it be reasonable to make it +12 to defense instead of +9?
Some suggestions are that they wouldn't boost the defense because it's unlikely that sound during combat would betray the wizard's location, so moving the sound wouldn't make it harder to find. Another suggestion was making it a group to make additional images, but the only thing I can think that would do would add additional misses, which seems to to me to be a bit OP.
The thing is, once you are nearly invisible, it is hard to make yourself more untouchable. The magi remains within one meter of its image, so broad strokes and lucky hits can happen (just last night in the game I was running, a NPC used that and a very lucky hit insta-killed her).
I don't think such spell should increase the defense, but there could an additional penalty to locating the magi, as the attacker could only rely on small detail like footprint, dust being moved on the floor, or eventually smell if the magi is rather "smelly".
To increase the defense, the image could be 5 meters away, making the mage nearly impossible to be hit even by wide strikes. However, it becomes more difficult for the image to act according its surroundings: moving through obstacles, talking clearly in the wrong direction, etc...
The attacker should quickly understand that it is just an illusion, but he still would need to seek for clue to locate the magi (see fighting invisibly, p 32 HoH:S).
I wouldn't allow "moves sound" to give an extra bonus, and if you're moving the image any further you might as well be using Veil of Invisibility, or at least its rules if you aren't good at Perdo. But as Tugdual says, a version with requisites to get rid of your shadown might be a bit better. (I guess that's CrIg, maybe?)
You could have a version with multiple images. Rough suggestion: this is confusing enough that the miss chance is higher for the first one or two rounds, but once someone is aware that none of the images are real, the penalty drops to +9 defence.
There's quite a lot about this in the Flambeau section of HoH:S.