I always play that way but after I talk to some players here I understood some people play it differently.. So I would like to clean some points.
If enemy shadow card effect say: enemy get +3 attack and I manage to discard this card (Gandalf staff for example) not cancel a shadow effect , just discard shadow card after the shadow card was revealed. So in this case enemy lose +3 attack bonus since shadow card not in play amymore right?