If he moves out of range they fade away only to comeback when he moves back in range
I like this. the idea that there are illusion buildings that take damage and give damage or do actual things in the game. And you need your character to stay within range of them, or they fade out & stop working. Then, moving back in range and they activate. I like the idea of there being traps, like a dozen turrets, and as the enemy troops approach, a couple of these conjurer characters approach at the sides, and dozens of defensive turrets show up.
I also like the idea that if another unit is in a turret's spot when the conjurer shows up, that the turret does not reappear/activate. however, as soon as they walk out from under it, it snaps into place. I also like crossing the Terran Satellite with this. How from a distance, you can see all things (including cloaked). Except that this would make the turrets visible to the opponent in this case, providing limited activation time.
Then the ability can double, where if you are being over run, you can deactivate it, and all the buildings dissapear into a deactivated state. If they are on fire, the fire will still be there when they re-appear, but no damage will be taken while they were deactivated.