FoxWander
Adventurer
This!
This is excellent advice that will probably do the most towards keeping such a campaign from falling apart. I've played in two "evil" campaigns and both worked because of this premise.
- The first was pretty much the OP's original idea- a 'reverse dungeon'. Our evil PCs took over a town/dungeon and became the "growing evil" that got heroes sent in to thwart us. Our "goal" in that one was actually us player's wanting to screw with the DM and take advantage of certain tropes he always used so he would stop using them! Also we wanted him to stop running adventures that were designed solely to derail/shortcut the campaign of the other DM (also a player in this game) who ran in this shared homebrew game-world.
- The second campaign was, oddly enough, our group of evil (and neutral) PCs trying to save the world. The DM set up a scenario that started with our PCs at epic level and our world was at the end stage of being destroyed by a magic-using, mutated, world-devouring tarrasque (basically Galactus). Just as the world was destroyed, our PCs finished a ritual powered by most of our life-force (it knocked us back to 3rd level) that would contain the beast for a year and a day. The ritual blasted us (and the beastie) across the multiverse. We awakened on the DMs homebrew world which he had set up as THE prime material plane- as in it was the source of ALL magic. If it was destroyed, magic everywhere would end. So naturally we had a very vested interest in using our year of time to destroy the beast once and for all to save it. But, it turned out, we all really hated that world (for various reasons it was a highly annoying setting to each of us). We had to save it as a whole, but we didn't care who or what we destroyed in the process.
Both were fun campaigns enjoyed by all (even the DM who ran the first one) that didn't fall apart because we had an overriding goal that kept us working together.
