Ok I see what you're getting at now and understand. ALthough sometimes killing off the skellies isn't such a bad idea...lol..although it would make bone walls way OP. As all I would have to do is put out a boneyard, a bone wall and kill something. voila 2 hours later it's still cycling through dead creatures. Skellie, it dies, new skellie, it dies.....
So yeah I see you point. Does it only cancel out one nightfall per one of these in play? If so that could be good rather than an instant nerf all nightfalls.
the only other way i suppose would be If nightfall is in play all Death|Darkness gain -1|-1 or soemthing like that but then it gets wieghty.
Good work.
Scyther