Chaotic Evil, I'd imagine, is not a common alignment to play. Why? Well, it's generally interpreted as "Kill anything you see all the time without any regard to anything", which doesn't really allow for much in the way of joining a party. To me, that's idiotic.
Sure, someone who did that would be chaotic evil, but not everyone who is chaotic evil is like that. Orcs are listed as 'usually chaotic evil', in 3.5. In 4e, if it lists alignments, they are probably the same. With the above interpretation, no orcs would exist, because they would be too blind with rage to even mate. Yet, orcs have functional tribes and occasionally armies. Why?
Chaotic evil just means that you care little for rules and less for altruism. A single orc, coming across a single unarmed human, with no witnesses in sight, would probably kill him. Why? Why not? The human has stuff, maybe some of it is worth something. The orc doesn't care about sparing his life; there's no reason to.
However, let's say a single, unarmed human approaches an orc tribe. He's approaching in the open, not hiding, and wearing the colors of a local citystate. The orc chieftain, or at least his advisor, would order that the human be left alone, as he is obviously a messenger. Yes, they are evil, and yes, they don't respect law with regards to killing messengers, but they are also likely self-serving and know that mercenary work can pay well, even for orcs. It's rare that someone is so devoted to creating chaos and death that he won't act in his own self interest when he can.
How do tribes of Chaotic Evil creatures even form? They form on the basis of self-preservation and greed. A big gnoll can beat up a smaller gnoll. The larger gnoll is now a leader of a tribe of two. He keeps his lesser kin in line with beatings and harsh treatment, and he slowly brings in others of his race, or other races, by the same methods. The larger gnolls in his retinue get power to control the smaller ones. On occasion, some gnoll will become powerful enough to kill the previous boss, and thus will show that he can control the group. There will be constant infighting and working to get ahead in the positions, but the tribe itself is still cohesive. Self-preservation is a powerful tool for chaotic evil races. Besides, gnolls know that a single gnoll has a hard time raiding a human trade caravan, but a pack of forty can do it easily.
What, then, about Chaotic Evil PCs? Assuming we are discussing a party of chaotic evil PCs, they are probably using the latter justification for the gnolls: power. Together, they can do more than they can separately. They can make more money, get more food, sleep with more women, whatever. This is what a good number of bandits do. Bandits are evil people, the occasional Chaotic Good Robin Hood not withstanding. They band together in order to have the combined strength needed to achieve their goals. In a party of Chaotic Evil PCs, all of the players should both be expecting the others to grab the loot and run, and planning their own way to grab the loot and run. They don't feel allegiance to their compatriots, and if they have enough money to achieve their goals, they are as likely to run off with it as to actually stay. Is this disruptive to a campaign? Yes. Does it immediately provide a possibly awesome adventure chasing down the now DM-controlled former PC, with that guy that you just met in the tavern (a new PC from same player)? Also yes. Bonus points to the PC that sets up a stronghold during play, documents it as a full dungeon with traps and henchmen, and then scampers off with the loot. Now there's an entire dungeon of enemies, topped by a suddenly more powerful and well-armed ex-PC!
What about introducing, preferably secretly, a new chaotic-evil PC into an established neutral/good party? You have to do this knowing that it will result in conflict eventually, and you have to know your players can handle this sort of pseudo-betrayal. Still, this can make for a lot of interesting roleplaying hooks.
Let's say you have a fairly typical "good" party. A Chaotic Neutral rogue, a Neutral Good Fighter, a Neutral Good Cleric, and maybe a Chaotic Good Wizard. The fighter dies in a dungeon, and does not respond to resurrection. The group, for some reason knowing that someone else exists that will join their group, goes looking and finds another fighter in a tavern or somesuch. The man seems a capable combatant, isn't a cringing sociopath, and agrees to join on for a full share. The new fighter introduces himself, talks about his past fighting injustice, etc etc. The DM perhaps requires a few secret bluff rolls, or just wings it if the party seems to believe the guy. The new fighter is Chaotic Evil, and is basically just joining up for the loot and chance to kill some things.
Does this new party member have to attack the other PCs? No, he doesn't have to. In fact, he shouldn't. He knows how powerful they are, and he knows that as the odd man out, he'd get slaughtered. What he wants is money and magical items. Maybe he stays on for a while, studying them, keeping track of their safeguards and their wealth. He might make a move to steal everything at some point, but he'd be sure to have an escape ready. More likely, the party would eventually see what he is, and force him out. The player signed up for this character to be lost the moment he put "Chaotic Evil" on that character sheet, but hopefully still had fun doing it.
If the Chaotic Evil fighter wasn't killing the party, how would they find out that he was chaotic evil? He's evil. No matter how hard someone tries to hide their moral core, parts of it slip out on occasion. He's unnecessarily abusive to captured monsters or people. He taunts injured foes, and takes great pleasure in dealing pain to his enemies. He verbally assaults NPCs, and occasionally runs into trouble with the city guards. Perhaps he even runs into the occasional law officer who recognizes him from some old crime, and has to talk his way out of arrest. There are a lot of things that can make for some interesting party dynamics here. The guy might even be worth keeping around after being revealed, just for his efficacy in combat.
Anyway, give some thought to Chaotic evil characters, and you might be surprised that they can be as nuanced as any other alignment. You may even consider playing one, just for fun. Game on!
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