I understood exactly what you meant by having the effect take place first. I do not want creatures being played to be altered, that would make the card almost 100% useless, since it would still only be a one time use, and unless you played a lot of creatures, hiding only 1 or 2 is kind of silly. Now using it on a field that has a lot of creatures is more effective, and can and WILL confuse people because not everyone has a photographic memory.
The cards effect and card type is exactly what I had in mind, to alter the creatures already in play. That I am refusing to change, but if you have any actual issues on it being too powerful, or the costs don't seem proper, then I will listen, but your suggestion to change the card how you said makes it almost a completely different card. And from your example, you make it into a 2 turn card, and for what the effect is, makes it worthless.
Since this is the final mechanic:
I think the cost is too high for the confusion of the inattentive. 4
|3
would be more appropriate even though it will sometimes be a dead draw/waste of quanta.
May I use the illusion mechanic to create a Darkness Creature?