Since the Shadows rules already state that once an attachment is brought out of shadows it has to be attached to a valid target… does the Response on Turncloack restrict it in any special way? It seems to me that if Turncloack is an attachment and the restriction isn't passive, but a RESPONSE, then, really, all that you're getting is that attaching to an opponent's character during the Challenges phase can be cancelled, while that's not the case if it's brought out of Shadows at any other point.
What am I missing there? If that's the case… that card suddenly becomes ridiculously powerful targeted kill during Dominance.