In the end of game screen, I can only see part of the description for the effect of wolf den. Also, after clicking twice on the "Description" label, it shows a japanese-looking character in the end. You can see it in the attachment. My screen resolution is 1024x768.
Edit: I changed the resolution to 1280x768 now but that didn't change much, you can see it in the second screenshot. I noticed for me it just says "exactly one of .", because I had no cards I had exactly one copy of in my deck. So in that case, something like "no unique cards in deck" would probably be better.