Is there a filter in the Hall of Beorn to search directly for cards with a shadow effect? I have not yet succeeded in finding one.

I believe there isn't...

Maybe @danpoage can make a search with that parameters.

http://hallofbeorn.com/LotR?Query=Shadow%3A

Results are limited to 100, for performance (and cost reasons), so I suggest adding other filters (e.g. CardSet) to narrow your search.

Thanks for your answers, but it does not seem to work for me. There are only Mountains of Angmar, Rolling Seas and Black Bats displayed, and the Seas do not have a shadow effect.

It seems to pick cards with the word "shadow" in the card text

@Amicus Draconis I believe this is the correct query: http://hallofbeorn.com/LotR?Query=%2Bshadow%3AShadow

Thanks @Seastan, that did the trick!