Opportunity Actions: Campaign Workshop – Betrayal
Benedict Arnold, Notorious Traitor
One of the keys to running a good campaign is keeping the players invested. A fantastic way to do this is to make character backgrounds integral to the major plot of the campaign. A lot of this can be done in character creation.
The idea for this came from a few board games I enjoy, most notably Betrayal at the House on the Hill and Shadows Over Camelot. These games, like D&D, are cooperative. Somewhat unlike D&D, though, these games involve a mechanic called the Traitor. You’ll see how this plays out further along.

Brutus, Betrayed Julius Caesar
During character creation, give every player the opportunity to add something to their character’s origin. We’ll call it the Dark Secret. Usually, players want to throw something like that in there anyway, and making it part of the character creation process gives these ideas a chance to come to the forefront. When everybody has a Dark Secret for their character, write them down on cards. These cards are your bible.
Periodically, give a player a choice: reveal their Dark Secret to solve a short-term goal, or offer a 10% session XP reward to keep the Secret, taking the more difficult path to success. Write these events on the cards, and this will show you to what lengths characters will go to protect their Secrets.
At some point (say, mid-Paragon, if you’re playing D&D), take the player who has proven they have the most to hide (by protecting the Dark Secret) aside, & tell them you’re thinking of revealing their Secret. Tell them that, as a result of their excellent role-playing, their character is shaping up to be the perfect choice for the campaign’s major villain. Tell them that the character won’t be taken away, from them, but will be going on a hiatus. Offer them the chance to become a new character, one that can even be connected to the old one somehow.
While the rest of the group plays on, this player can be helping hatch out plots for the villains continued rise to power.
When the campaign is coming to its end, find an appropriate exit for the sub-in character. Noble sacrifices handle the job nicely, or they may even betray the party, becoming a henchman of the antagonistic character. Either way, the player once again takes control of his original character, and plays out the final confrontation.

Your Job:
What does this mean for the DM/Game-master/Referee/Etc.? For one, you will not be stuck looking for plot hooks. If you can’t think of one, tap the Traitor. Use their backstory to motivate the campaign arc. That player will get a sense of satisfaction watching their plots unfold, or be challenged by their unwravelling. It’s then the DM’s job to fill in how the world reacts. How do oppressed villages feel about this new tyrant? What dark forces align themselves with this malign person? Do they remian loyal, or turn on their master at the height of the final conflict, forcing the traitor to re-align himself with those he betrayed? These and other questions are all yours.
I think this concept is great, and with the right group of players, there can still be enough twists (especially the big one) to keep everyone entertained.
Thoughts? Suggestions? Let me know!
RPGBN
I have a player hiding a dark secret (she’s a spy for an enemy of the group’s house) but I really don’t like it. Betrayal is a “cool” idea, but I don’t think it’s really good in D&D. The problem is, D&D is a cooperative game, and the players expect it to be such. In the end, I worry that this betrayal will feel more like a “real life” betrayal, and lead to hurt feelings. Have you tried this idea in practice yet? If so, how did it work out?