We tried a campaign with an evil party. They did a good job at not being your average high school-screw the other character- evil, the players were totally who cares about about collateral damage and ends justify the means evil. And they were off to save the world. I know it sounds odd. But Evil folks like the world too and dang it if somebody is going to screw it up, it’s going to be them not some tentacle faced aberration. They actually started to role play and then this little scene played out:
Evil Wizard: I just learned that there is a powerful magical artifact hidden in a Good temple.
Evil Bard: Why don’t we just ask them for it? I’m sure they want to save the world too.
Evil Cleric: No way! Remember last time. That they saved the world. Did they ask us for our artifact? NO! They just stormed the place. Killed everybody, took our artifact and anything else that wasn’t nailed down.
Evil Fighter: He’s got a point. I think they even stole the furniture. What were they going to do with that?