My first reaction was "that sounds stupid", but after reading some comment from Donald X about designing kingdoms for it, I think it could be pretty fun. Sort of like solo challenges, except from the designer.
I have not actually seen an implemented version of the campaigns, and my details there are sketchy.
A campaign (for a full or half set) consists of 20 levels, each level is a game with 10 cards as usual. I picked out the 10 cards for most of them, but not for the main set / tutorial, and not for a few levels on some of the other ones. Basically when I first saw them I was displeased with how slowly new cards were introduced in them, and I ended up redoing most of the levels to fix that. And they hadn't done all the sets so I just did the other sets. There are a few I didn't change though.
However there is more to a campaign level than that - in particular I think the starting decks may vary by level. Every nth level is a "boss" in some sense, I am not clear on that either. There is story text. I didn't do any of that work, I just picked out the cards.
There are achievements, that is unrelated, and they will not be in the initial launch. There are generic achievements, I don't know what those are, and there are per-card achievements, and I picked out all of those, with help from playtesters.