Not "Evil" for the sake of it, but "complex". Driven.
This. You can stop all discussion from here on out, this is all you need.
Not just complex, evil should be rewarding. Why people steal or work for mafia? They do if for profit. If the whole benefit is having sex with some drow who sounds like an old truck and wants to kill you afterwards then it is not exactly rewarding. It seems like a bad investment.