There comes a point in most Game Masters’ lives when the game they are running has outlived the system in which it began. Sometimes that’s the result of a new set of rules coming out that make the game easier to enjoy. Other times it’s because the old system is incredibly dense and difficult to get into whereas the new system is much easier on new players, who suddenly make up a significant potion of the people in the game. Maybe everyone got a little tired of the old system and agreed the new system is going to be much more fun to play. Whatever the reason, you now face the difficulty of helping your players transition from one system to another while also trying to change your notes for future sessions, bad guys, and house rules so they all fit into the new system. A monumental task that makes creating a dungeon seem like a simple job.

I’d recommend doing this during a hiatus or at least planning on missing two weeks worth of sessions since you don’t want to go into this half-cocked, especially if you have a lot of house rules. If you’re good at Fudging It, you can skip the house rules and the overall process will be easier, but you probably shouldn’t skip if you can avoid it. Having house rules the players depend on changed to the new system is important because it helps them set expectations for how things have changed. For a lot of systems, these kind of changes are pretty simple. Converting a Dungeons and Dragons campaign from edition 3.5 to Pathfinder is a simple task since Pathfinder was heavily influenced by 3.5 and most of the numbers are the same from one game to the next. Changing 3.5 to fifth edition is not nearly so easy, even if it seems easy on the surface. House rules about critical change because there is no rolling to confirm critical hits in fifth edition, but that’s easily resolved since you would just drop house rules about confirming critical hits. House rules about treasure, though could change. Fifth edition magic items operate on a very different scale than magic items in 3.5, and the same goes for pretty much any numerical roll. Skills have lower numbers and the difficulties of checks are lower since rolling high in fifth edition is rolling a thirty. If you’ve got a bunch of custom checks mapped out for skills or actions the players regularly use, you’ll definitely need to rework those.

Additionally, there are a lot of balance changes that happen from one game to another. In edition 3.5 of Dungeons and Dragons, fighters tend to be focused on combat skills or utility. In fifth edition, what they focus on changes depending on their specialization and they can wind up as anything from excellent tanks to damage-dealing monsters. Someone with a highly specialized build will need to do a lot of changing as well, perhaps to the point of basically having an entirely new character. If you have prestige classes in 3.5, chances are good that you won’t have them or anything directly related to that specific skill set in fifth edition. And that’s from one edition of a game system to a newer edition. At their core, they’re still the same d20-based game, but what if you make a bigger change?

If you’re running a Dungeons and Dragons campaign that focuses mostly on roleplaying and storytelling, your players might find themselves frustrated with combat and certain skill applications since they tend to bog down a bit once it is time for everyone to start rolling dice. If your players don’t particularly care about the system you’re playing, it can be incredibly beneficial to switch to a Fate system since the skills and combat are much more narrative-based and tend to resolve much more quickly. However, there isn’t a clear class system and the conversion from class levels in Dungeons and Dragons to skill points(the main display of a character’s power) in Fate isn’t a super clear one since even the skills don’t really represent the abilities a Fighter or Wizard might have. It can be done with enough work and the thoughtful participation of all parties, but it definitely won’t be easy. There are other d20 systems out there as well, some closer to Dungeons and Dragons and some decidedly less so, that could be used to take the game in a more Sci-Fi direction, but converting to them is going to run into a different version of the same issue.

While you’ll be missing a couple of sessions while you work out how most of the numbers, power levels, and custom rules will convert, you should include the players in the process. You can use normal session time to do it, or you can start a texting group to get their thoughts. It’s good if you find a way to convert the numbers that makes sense to you, but you also need to consider the players and how they view their characters. No one is going to want to go from feeling incredibly powerful to feeling weak or useless. You can avoid that by working with your players and offering solutions to their feelings of powerlessness, even if it makes the character seem more powerful than they should be. For the most part, it’s fine if the players wind up with powerful characters and it’s even possible that something that seems incredibly powerful will wind up not being as useful as you thought once you start playing again. The best part of any kind of conversion is the knowledge that you can always go back to tweak things as the game continues since no one in their right mind would hold it against you.

Changing systems is a lot of work and, if you’re open and clear about it with your players, they’ll help you find solutions and be more ready to forgive any mistakes that crop up while you’re still ironing out the fine details.