My understanding of this game is that it's co-op, except for a 'jerkass gm' who does his or her best to kill the intrepid adventurers. It sounds like a lot of fun, reminds me of Diablo or other hack-and-slash games. A few questions though:
1. Are characters persistent? Do they gain experience or capabilities over the course of multiple playthroughs?
2. Are any of the expansions basically necessary for a full game experience?
3. Do the expansion campaigns append to the end of the core campaign i.e does it make sense to go through the core one, then do an expansion, possibly with the same characters, and so on, until you get bored?