Finally played scenario 3 last night, and this question came up.
The text on the Nazgul card states that "after the shadow effect resolves" (not shadow card), the engaged player removes 1 character.
Now there are 3 ways we interpreted this.
1. Since the card states shadow effect, if the nazgul receives a shadow card with no effect, his forced ability does not activate (no effect to resolve)
2. Shadows cards with no shadow effect still resolve (with no effect), so his forced ability does activate
3. It's a typo, and should read "after the shadow card resolves", which give the same result as #2 above.
We went with the #1, since a shadow card with no shadow effect never resolves. To us it seemed the most literal interpretation.
How have others played this?
I searched the forums, but couldn't find an answer.
Thanks,
Don