Is there anything more devastating than the threat that comes from within? The friend that drives the dagger into your heart with a warm, familiar smile? This is a cautionary tale on the ruinous powers of the PC who, unbeknownst to their party, plots their downfall.

As a fairly experienced GM, I spend quite a lot of time thinking about what a GM’s responsibilities are, both to their players and to their games. And I think, beyond making sure fun is definitely had, we might be responsible for inducing truly breath-taking moments of ephemera at our tables; Those times when you can almost hear the table humming with a warm anticipation for what will happen next and those golden moments of roleplaying occur that become legend.

Now, while I don’t think it’s possible to force this energy out of your players (it would certainly ruin it if you could) I do think that a good GM can certainly offer these wonderful moments somewhere suitable to stay. With appropriate prep, an energized cast of players, and perhaps a devious trick up our sleeves, the stage will be as set as it can be.

With that said as a GM you might want to consider conspiring with one of your players to truly shock and amaze them with your tricksy wiles and clever story-telling. To introduce a traitor builds a certain amount of dramatic irony and unpredictability into your games that will allow you to experience a level of suspense that is usually exclusive to the players. For the first time you won’t have control of the campaign’s general trajectory. Your fudged GM rolls (we all do it, don’t worry) won’t be as concealable. There’s a greater element of the unknown than ever before.

That special energy comes mainly from knowing that any moment your conspirator can turn the entire game can turn on its axis, and that’s truly exhilarating.

Wot Happened When I Done It

I had been running a campaign of Call of Cthulhu (6th ed) with a new group for about a year. It was their first ever campaign, but my third. They’d taken to the mysterious game like Scooby and The Gang, with a number of slightly-too-lucky scrapes and a range of miraculous solves that perhaps were too easily won. I’d finally come to feel it was about time that the group moved onto pastures new. I struggled for a few weeks with the right way to twist the cruel knife of Eldritch doom and truly wow my players when an impish idea occurred to me: What if the one to finally bring this oddball cast to their unspeakable doom was one of their own?

(I say this like this was my original idea, but I think I was actually inspired by this legendary thread about an ingeniously evil Warhammer 40k: Deathwatch traitor which  I’m pretty sure I shared gleefully with everyone who I thought would listen around that time  (including the players I’d come to subject to it.)

So I set about figuring which of my players and which of their characters would make the best soil for this traitorous seed. There was Lily the Mild-Mannered Madam, Boo the Infernal Enigma, Raga Muffain the Unhinged Aristocrat, and Crafty Joe the Criminal Kingpin. There was an obvious choice here.

Joe was a table favorite, so he was out I needed to make sure he met a more dramatic end. Boo had had their own flirtations with villainy in the form of an Elder God possession, so would arouse suspicion. Lily would’ve made for a decent twist of character, but struck me as slightly too far out of the left field. Raga Muffain was what was left. The clear winner, actually. His background was hazy, and his character was suitably deranged everything I needed to rewrite Muffain as a hideous Eldritch villain.

So I worked in secret with Raga Muffain’s player to adapt H.P. Lovecraft’s short story, “The Rats In The Walls” into a dreadful tale of Muffain’s monstrous desire to resume a program of human cattle breeding that his ancestors had started decades earlier. He was to use the other investigators as his prize progenitor stock after luring them deep into the vast catacombs lying dormant beneath the family mansion he feigned complete ignorance of.

As I gleefully engineered the trail of breadcrumbs that would lead to their demise I didn’t spend much time worrying about whether the story would be particularly fun for my players. A possibly fatal mistake in hindsight, and maybe the whole scenario would’ve ended right there on the page if I did, but I didn’t.

To cut a very long scenario write-up short. The story ended in a cavernous field of human bones. Deep below the mansion, the light of an impossible spire built by a race of Eldritch mutants served as an unholy beacon as Muffain sprung his trap to subdue the investigators with the help of his shifty butler. Fortunately for the investigators, the crazed would-be human breeder was gunned down by Crafty Joe, our resident super soldier and all-around table celebrity. However, Joe himself became a tragic casualty in the crossfire, leaving Lily and Boo to pick up the pieces and flee as hordes of hideous man-creatures chased them from the caverns.

The silent fury that permeated that room when Muffain betrayed the group and caused Joe’s death was as glorious as it was abysmal. For each part of me that was stoked to have pulled it off, like an expert jewel thief, other parts were worried I’d gone a little too far, like an expert jewel thief that had found his prize to be haunted by demons. In betraying my players’ trust by disrupting the GM-As-Adversary/Players-As-Allies norm, one that I’d never really breached with this group prior, I wondered if I let them down in some way.

The answer’s complicated in quite a few ways. In other ways the answer’s a lot simpler. Yes. Yes I betrayed their trust a little (or maybe a bit more than that.) They were right to be pissed. In saying that, I don’t think I regret it. It was one of those landmark moments in my history of running games. And within the group, most of whom still come to my table to this day, there’s a great deal of nostalgia about that time I employed a traitor. There’s also a lot of rage. Like, a ton of it, actually.

So … Should I Try Introducing A Traitorous Player?

Well, that’s a very good question that I asked myself. Ultimately, you know your group, their characters, and the tone of your game best, so you know if it would work for you. And most importantly you know whether you’re a GM or a player who could pull it off.

In my case, I think my conspirator and I were both wildly successful and critically catastrophic in different ways. It certainly became legend at the table. And we certainly provoked a level of that special roleplaying energy I strive for as a GM where players make critical, awesome decisions and everyone holds their breath as they land (or don’t land) magnificent rolls. But we also really pissed them off. Like, seriously. To a level that was less “fun and impish” like I wanted it to be and possibly more on the “upsetting and awkward” side. It definitely ended up somewhere in-between. I still don’t know if it was worth it three years later.

So I’d say if you’re still curious that you should try it, but be cautious. Keep remembering to think about what your players want, and what they like about the game. Try to balance that with what you want. Keep them in the forefront of all your plotting and scheming, no matter how nefarious it is. Because, while some RPG systems set the GM up as an adversary (like Call of Cthulhu), you don’t want your players to plainly hate the game you prepare for them — that’s just a waste of everybody’s time.

So if your players are enjoying roleplaying a goofy gang of investigators who love to triumph over the endless Eldritch horrors that should by all rights be squishing them like bugs … maybe just let them? You probably shouldn’t ask the shadiest member of the Scooby Gang to lure another PC into the woods and later toss their severed head into the Mystery Van.

Although who am I to judge? Maybe a good ol’ fashioned backstabbing is exactly what your campaign needs right now. Maybe you’ve always wanted to see what Shaggy would be capable of with an axe in hand and a murderous murmur on his mind?

Let us know if you’ll be trying a traitor out in your campaigns, or share your own traitor stories in the comments!