Wow, this thread got out of hand really quickly! Back to original topic.
If you can't cancel shadow cards, how about discarding them? I built Gandalf-Elrond-Merry deck with Vilia and used Gandalf's Staff to discard shadow cards from enemies in both day and night. After my threat got to dangerous levels, Merry was able to hold it until I was finished. In the end, I used Flame of Anor to blow that wolf into oblivion. Is this strategy ok by the rules?
You can definitely discard them, but just not cancel them once they are revealed.