You wouldn’t want me in a “proper” evil campaign. Most people have zero concept of what actual evil looks like. They think is something edgy or cool. It’s not. It’s cruel, vindictive and ultimately nihilistic.
Well as a Catholic I have to disagree - while yes that's probably fine Evil Outsider - aka demon description, I think most of human evil is very... banal, almost boring, not really even criminal.
Of course in D&D it's all much more murky - but I prefer a way when you have a lot of perfectly socially adjustable people whose current karmic-sheet says EVIL (as usually I like to treat D&D alignment in a karmic way more than = oh look there is only 9 personalities).
In 3,5 Ultimate Scoundrel there was good example of it - and I love it - they counted Jack Black's character from "King Kong" the fat director who wanted to film King Kong - as Chaotic Evil, and I was like - excellent! He is no mad cultist, he is no mass murderer, he is not cruel or vindictive - he is just sort of uncaring about consequences in a massive way as long as his purpose if fullfilled.
In other way - you do not need to play Evil Incarnated to play character with evil alignment in evil campaign.
But I agree it's usually not cool or edgy.
See, the thing about playing a “goody-two-shoes” is that you care about a lot of people and help alot of people. So I told the DM that if my goal is “hurt my good self as much as possible” they wouldn’t stay and fight... they’d immediately teleport away, leaving their mirror allies in the lurch and start systematically murdering everyone my PC had ever loved or helped (which included a lot of the DMs favorite non-combat NPCs), get a copy of the animate dead spell to turn everyone killed into skeletons (because in 3e your soul can’t move on to the afterlife or be resurrected while it is undead) and then scatter them with commands to lay buried and motionless for eternity so their souls would be trapped forever and denied the afterlife. Then I’d send my PC a message via spell of what I’d done and that if they ever helped another soul I’d do the same to them.
That's absolutely wonderful idea - but then you were playing very malicious mirror clone, not just evil dude like dunno Edwin or Eldoth from Baldur's Gate.
I play only good PCs not because I don’t know HOW to play evil, but because I cannot understand why anyone would ever WANT to.
Simply because well dependent on how your team understand alignment because I'm sure some would count what I'm gonna to say as barely Neutrals - there are multiple characters in stories I count as Evil - that are no looney, vindictive, mass murderers. Outsiders are literally made from Good and Evil. Mortal beings are not.
Walter White was evil, yet he still risked his life and fortune for his wacky sidekick (to some point at least), Darth Vader was quite way gone, but still cared about his family.
Precise interesting point about Evil-Doers is that they are not evil to everybody. And many are perfectly suitable to teamwork - still Evil in Alignment Chart.
And why would you want to play it? To explore such uncertainities. Duality of man. Unfairness of judgement. To explore how in many ways evil, sin, corruption is not this blatant Satanic choice to become bloodthirsty monster but slow, slow, slow corruption and even in corrupted man some aspects corode fast, while others can survive.
And I mean even in most blatant way you can make LE mercenary that always hold his end of deal.