I just want to chime in that even D&D roleplayers seem to get confused about what evil is and play it like some kind of chaotic psycho. The fact is you can play an evil character who is actually nice, under most circumstances, but puts his own needs first. In other words, an evil character might help the Grove out, if he thinks he'll get more out of it than helping the goblins. And thus I echo that to be interesting and to be tempted to make evil choices, the player needs some sort of incentive in place other than "I want to kill all the good people teehee."