So, let me throw this out there first, I love Shadowfell. Love it. I want it to be awesome. SO, for my two cents, a war between Vecna and the Raven Queen is great grist for the mill. In a lot of cases the appearance of a well worn name like Vecna would turn me off, but not in this case, in this case I think he stands pretty clearly for one side of that. There's a ton of great material out there for Shadowfell, and adding a war just makes it better.