The thing about villains in roleplaying is having a character solely meant as A Villain generally doesn't work as well, simply because no real people are as malicious as that might require. Instead, you wind up with several people serving as the villains in a particular timeframe. So we need to define what we mean by villains, what role they can play in roleplaying, and what the pitfalls are in the first place.
Malice, antagonism, and villainy
When we talk about villains, we're generally talking about them in the context of a story. There are real-life villains, yes, and if you want to really confound someone, you can use the original meaning of the word "villain" and see if anyone knows what you're talking about, but for this column we're looking at stories. Kefka, Saren, Illidan -- you get the idea.
In a roleplaying context, the field of villainy actually gets broader than usual. Most fiction either features protagonists who are basically decent people (Star Trek: Deep Space Nine has several morally ambiguous individuals who still come across as fundamentally good) or at least much better than their opponents (no one on Lost avoided screwing at least one person over, but the villainous characters were magnitudes worse). You're supposed to be cheering for the main characters, after all.
Roleplaying gives you the chance to play people you won't cheer for, though. That adds a whole new dimension.
The upside is that villainous characters can be of two different types. You could have a malicious character or you could have an antagonistic character. They're both villains in the strictest sense, but they're not the same sort of character.
A malicious character is fundamentally broken in some way, the sort of person whose moral code allows him or her to do awful things without guilt. In the D&D model, these are the characters whose alignment is some flavor of Evil. Assuming you want to create actual characters instead of cartoon villains, malicious characters still have reasons for their behavior, but these reasons pale in comparison to their outright awful activities. These characters frequently wind up being villains because no one really wants Baron Von Puppymurder to succeed. He's not a nice guy.
An antagonistic character, on the other hand, is just a character whose goals are mutually exclusive to those of another character or group of characters. Consider a Charr in Guild Wars 2 who wants to tear down the last ruins of Old Ascalon. He's going to be an antagonist to characters who want to preserve the ruins, but he's not doing it out of malice so much as a desire to finish claiming the land for the Charr instead of wallowing in human wreckage. Even if you don't think it's a laudable goal, it's just a goal that doesn't fit well with the goals of anyone who wants to preserve the land as it was.
This isn't to say that malicious characters can't be antagonistic as well; it is possible to have a character who is one without being the other. The villain of a given arc could just as easily be a decent person in an awkward situation or someone pushed to extreme means for an otherwise laudable goal. Perspective plays a bigger part.
How it works and how it hurts
The big advantage to having a player behind a villain is obvious if you've seen pretty much any story ever in the history of everything. A conflict wherein one side is simply stymied by an unseen force isn't half as interesting as when you have both sides in full view of those who choose to look. The potential interplay between the villain and those being antagonized by the villain is part of the fun.
Unfortunately, as mentioned before, in most stories the villain is pretty roundly dealt with by the end. As my favorite college writing professor once told me, we're conditioned to want every conflict to end with the hero fighting the villain on a catwalk above a slowly rotating fan into which the villain will fall by the end. This is a problem with roleplaying, as regularly killing characters off is not terribly viable.
It's also problematic when the villain is less malicious and more antagonistic. Malicious characters usually deserve what they get; when my murder-happy Rogue in World of Warcraft met her end in a brackish pool of water in Duskwood, it felt entirely appropriate. But she wasn't just an antagonist but an actively awful person, someone who had spread a lot of misery for no purpose beyond her own momentary amusement. It's hard to see a Charr nationalist as deserving the same fate as someone who shot a man in Ratchet just to watch him die.
But purely antagonistic characters have a different issue. Given the idea that everyone can be an antagonist to someone, eventually everyone will be. This is the domain of the soap opera, where no one trusts anyone else because everyone has at some point done something awful to every other cast member, and when a new cast member shows up, he or she will be told about how Person X did all sorts of terrible things.
So we've established the biggest problem: You don't want to let these characters die off, but at the same time, you don't want to let these characters just stick around endlessly. There needs to be a sense of completeness, of conflicts resolved. So how do you manage that part?
I guess you'll just have to check back here in two weeks for part two. I can be pretty antagonistic myself sometimes.
Feedback, as always, is welcome down below or via mail to firstname.lastname@example.org. Next week I'm discussing artifacts and items of power, and the week after that I'll be talking about some villainous templates that work well in roleplaying.
Every Friday, Eliot Lefebvre fills a column up with excellent advice on investing money, writing award-winning novels, and being elected to public office. Then he removes all of that, and you're left with Storyboard, which focuses on roleplaying in MMOs. It won't help you get elected, but it will help you pretend you did.