@Mr_Bean987 Your trigger leaks and isn't made for dynamic spell since you the region at the constant position location. Creating a dummy is completely not needed, since there is already Permanent Invisible ability, and therefore makes things easier to do. Further more, what I get from this explanation is that units inside can do whatever they want and invisibility does not break unless they leave the bush - if it's normal invisible they will break as soon as unit start any action.
@4rankie
It's quite complicated because of idea inside the bush and sharing vision between ally-enemy. I can take this as request, but will do tomorrow since I don't have editor around. How the bush is created? It's just standard ward-summoning?