A good RPG campaign usually takes on a life of its own. The longer you play, the more the characters, the places, and the events of a game overshadow the rules which you use for the game. Ironically, it’s this shift in importance away from mechanics which can sometimes reveal that the mechanics you’ve been using aren’t going to work for an important part of your ongoing game. In another situation, your campaign has taken a dramatic, albeit temporary, turn. Your grizzled heroes find themselves masquerading as schoolteachers, or your starship crew finds a rip in the space-time continuum, or your cyberpunks have to chase a villain into a virtual reality game. Whether it’s a mid-story diversion or a permanent change, sometimes you’re going to want to jump systems.

RPGs are intended to be self-contained, and unless you’re playing games from a movement like the OSR which prizes compatibility and portability, you may find that moving elements of your game from one ruleset to another is surprisingly difficult. Conversions are imperfect and, given different approaches, a close numerical conversion may make something that feels completely different. Since you feel the need to change the underlying mechanics of the game, though, change should not be a bad thing…within reason.

There are two different scenarios for jumping systems: doing it temporarily for a specific conceit or adventure, and permanently shifting the campaign from one system to another. Both of these scenarios have their own complications and challenges, but both can potentially enrich a campaign if you pull them off.

Temporary System Jump

There are tons of tropes which place fictional characters in wildly different situations than the ones they’re used to. Consider Star Trek: The Next Generation. The “holodeck malfunction” episode is a classic (if perhaps overused) trope where the crew of the Enterprise finds themselves in a wild, not very sci-fi situation. If you were running a Star Trek campaign, you might find that your ruleset suddenly is lacking when the word of the day is ‘Sherlock Holmes’ rather than ‘Captain Picard’.

The starting point for this sort of system jump is to treat the game like its own one-shot or short campaign. Pick a system for the spin-off, don’t worry about its closeness or compatibility with what you’re already using at all. When it comes time to rewrite characters, you can either ask your players to rewrite their sheets, or you can do it yourself, but don’t worry about 1-to-1 conversion so much. You’re essentially re-imagining the character for the new setting, rather than converting them.

As an example, I did this exact sort of system jump recently when the characters in a game of Eclipse Phase I’m running went into a virtual world to reason with a super-intelligent AI. The AI had evolved from a child’s toy, so I decided that the virtual world it would construct for itself would be one of stories, fantasy, and whimsy. Knowing I wanted mechanical support for whimsy, I chose the most whimsical system I owned: Troika. Instead of changing any of the rules, I gave the characters average stats and had them roll random backgrounds with the justification that it was based on how the AI perceived them in their first meeting. Did it entirely make sense? No. Did it make enough sense for the players to engage with? Yes.

The last step in a temporary system jump is going home, back to the main ruleset for the game. Make sure that you’re awarding experience that carries back to the main game, and if applicable, be prepared to convert anything the characters take with them back to the main storyline. This wasn’t an issue for me where the sideplot episodes were taking place in a virtual world, but if your conceit involves something more concrete, it may be important to know that your starship captain picked up a broadsword.

Permanent System Conversion

Sideplot system jumps can spice up a campaign and let you do things outside the typical range of your core mechanics. In some cases, though, be it hypothesis-testing with your ruleset choice or a permanent shift in the timbre of the campaign, you need to offboard more completely into a new system. Whereas dramatic shifts in mood and mechanics are part of what makes short and temporary system jumps fun, moving permanently to a new system takes a bit more care. First, don’t rush. If you’ve just begun a campaign and feel like the mechanics don’t match, make sure you’ve given the current rules a fair shake. My rule for any new game is three sessions before either making dramatic changes or, in some cases, binning the game and starting over. Three sessions is long enough to figure out if your feeling about the game is coming from the game rather than a rocky start or one bad meeting. If the campaign has been longer going and you feel like change is afoot, make sure you know what you’re trying to accomplish by switching systems. If at all possible, write an objective statement, something in the form of “I want my campaign to be more/less x by having rules that are more/less y”. If you have multiple statements of that form, that’s even better. If you can’t come up with one, it’s a sign that you don’t yet know how switching systems will actually help you accomplish a goal for the campaign going forward.

In both scenarios, the false start and the mid-campaign shift, once you feel certain that a system switch will improve the game the next thing to do is talk to your players. If you’re running a short spin-off it’s usually fine just to tell your players that (provided the content and themes are consistent with what was already agreed upon), but if you’re changing up the whole game you need everyone at the table on board. Even before expressing specific preferences, many players will feel that they have invested in a system given enough time playing and will have misgivings about having to learn a new set of mechanics, even if the characters and setting stay the same. Ultimately, it’s your job to convince your players, but the most important thing you can do going into this is cultivate a willingness to back down. While there are exceptions, the most common reason a GM wants to change up a game is because motivation to continue the game in its original form is flagging. If you drag unwilling players into this process, you will almost certainly kill the campaign. By having a conversation about your feelings with your players, though, you may come across another method to give the campaign a second life without having to jump systems.

If everyone’s on board with the system jump, start the process with a second session zero. This will be nowhere near as long as an introductory session zero, but use it as an opportunity to go through character conversion together and answer questions about the rules. While expectations and ground rules you set in the first session zero likely haven’t changed, this gives an opportunity for everyone to be prepared as to how things will go. As you start to play, make sure that in-character you’re picking up where you left off. As much as possible, conversions should account for any advancement that’s already occurred and provide characters with the same or equivalent items and abilities that they had before. Now is not a great time to run your “everyone’s in prison with no gear” sidequest you had planned.

I personally have done this sort of system conversion twice, both times as a player rather than a GM. The first campaign was using Interface Zero, a Cyberpunk game written for Savage Worlds. The GM and I had both pledged to the Kickstarter for a Fate version of the game, and given his personal preferences the GM wanted to convert the game using the Alpha rules we had received as backers. The conversion was easy enough (it was basically a dual-statted game, especially in the playtest version), but the other players were a lot less familiar with Fate. While this conversion was as easy as a system conversion can get, there wasn’t really a reason for it and it’s hard to say if it made the game better, even if it didn’t make it worse. The other time I was involved in a mid-game conversion like this was in a game of Mage: The Awakening. The GM was frustrated at the fact that the magic rules did not in fact work like the rulebook implied they worked, heavily penalizing improvised magic while simultaneously stating it was the main avenue by which Mages operated (a vast gulf between implied setting and how the rules actually work is a consistent issue with essentially every product in the World of Darkness line). So, instead of wrestle with the magic rules, the group sat down and converted the game to Fate, using the Arcana in the game as a basis for a magic system that used Fate’s skill pyramid for the mechanics. The game ran smoother, characters were more magical, everyone was happy. Here, there was a specific problem to address (the magic system), and a specific avenue that addressed it (the Fate hack we wrote). As a result, the outcome was more positive.

With the sheer number of mechanical approaches to role-playing available, it’s unsurprising that many campaigns come across situations that are best solved by adding a new system to the mix, either for a temporary jaunt or for the long haul. The key to making these situations work is to lean into the justification for bringing a new system into the fold: for a temporary “hard right” into new mechanics, worry less about alignment and more about making the new game shine for the short period of time you use it. For a more permanent shift to new mechanics, reflect on your motivations, and then get buy-in from the whole group to ensure a harmonious transition. No matter what you do, be sure to consider what’s best for your campaign, as the campaign is an entity that transcends the rules you use to run it.

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