How to Design a Custom TRPG

Much of the world of TRPGs--and much of this site, for that matter--is about Dungeons & Dragons. But there are many other games out there which provide different experiences for players, both well-known in the world of TRPGs and relatively unknown. What matters with a TRPG system is that the game's rules support the type of experience you want your players to have. And you can create your own system to meet the needs of your campaign and your players with a bit of time and attention; all it takes is thinking about what the players should experience. Read on for a guide to designing your own tabletop roleplaying game. 

I personally have created two tabletop games from scratch. I want to keep my descriptions of them here minimal, as I want to be able to retain publishing rights for later, but I will provide examples by way of these games in addition to directing the creation of a brand new TRPG system, one which revolves around the solving of mysteries (something near and dear to my heart). The first step is to devise a setting. You want something that is somewhat unique. For my first custom TRPG, which I call Algernon's Tower, I wanted a high-flying, spectacular combat system that allowed the players to creatively use their abilities. So Algernon's Tower is about combat, and in order to provide a variety of settings to enrich combat, I set the game in a dizzying tower where each floor of the tower provides a different setting: a lava level, an Old West level, a creepy museum level, etc. The second game I created I call A Time and Place, and it is dedicated to the concept of time travel; players choose a time and place from a set of options and can play sessions in three different time periods in that setting, trying to use time manipulation to creatively solve problems. The game is supposed to feature the setting heavily, so I chose places and time periods that would be broadly appealing, such as 1750s London or 1870s San Francisco. Finally, we have our to-be-designed system involving a mystery concept--we want a unique setting that also serves the mystery format. We might choose Victorian England for the game, casting it as a classic Sherlock Holmes-style game. We might similarly choose 1930s America and run a film noir-style campaign. But for the sake of making something that is more unique, let's pick a less reality-based setting. I am going to go with 1970s California; that way, we get a more modern setting that still doesn't have the narrative-destroyer that is the cell phone, and the setting is broad enough that practically any story could fit into it. 

Next, we need to consider win conditions and lose conditions. For some games, this is simple: as in Algernon's Tower, winning means being the best at combat, and losing means being defeated. It's more nebulous for A Time and Place; the GM will select a certain condition for winning, like "prevent such-and-such disaster from happening," and the players win when they prevent it; because the players can time travel, there is no such thing as a real loss condition, only more time spent trying to solve the problem. For the mystery system, which we'll call Truths for Sleuths (TfS) from here out, we need to know how the players win or lose. Let's say that the players must solve the crime correctly before a certain deadline in order to win; dying, identifying the wrong suspect as the perpetrator, or running out of time constitutes losing the campaign. 

Then we get to my favorite part of the design process: mechanics. This may be a surprise for regular readers of this site; I am a very storytelling-and-roleplaying focused GM, so designing numerical values is not exactly my wheelhouse. But it is very fun to determine mechanics because this is where your game really comes to life. You decide in this step how the players engage with challenges, and that means a great deal to the players. There are two main elements to the mechanics you'll need: player abilities and game mechanics. Let's start with abilities. 

In Algernon's Tower, players are outfitted almost entirely along the lines of combat. I created a series of five attributes (Strength, Dexterity, Knowledge, Thought, and Socialization) with five skills under each attribute (hit points and melee weapons under Strength, reading others and screen presence under Socialization). [Screen Presence refers to the fact that the fights in Algernon's Tower are broadcast live on television, and there is a mechanic whereby players advance through their powers by attracting more viewers.] Between these 25 skills, every action in combat should be represented. This is a system, which like most TRPGs, has a set selection of skills that the player chooses proficiency in. Your system doesn't have to work like that, though: in A Time and Place, the players choose their own skills altogether. It's a relatively simple system. Each player starts with a pyramid, with one slot at the top, two on the next rung, three on the next, and all the way down the the bottom. The pyramid has six rungs--one for each type of dice included in a standard set. The player places their most proficient skill in the top rung and rolls a d20 for it; the two next-most skilled areas go on the next rung down and roll d12s for their checks, and so on down the line. Players can choose any skill they choose; the more specific, the greater their successes, and the more broad, the lesser their successes (all as a mechanism to balance narrow versus broad skills). Now we need to design the player abilities for TfS. 

The most important thing in designing player abilities is in asking how they serve the players. This means we need to be thinking about how people will actually play the game, and that means you'll probably need to playtest your game to ensure that you've covered everything. Before you get there, though, you have to make some educated guesses. Let's shoot for a system that's somewhere in between Algernon's Tower and A Time and Place, a system that allows the players to use an array of skills, but with enough structure to allow for the creation of unique characters. For that, let's have a small number of attributes to work with and a slightly larger collection of skills related to them. I'm imagining three overall detective archetypes with a handful of skills underneath them, perhaps four or so skills per archetype. Let's go ahead and fill in those details.

For our three archetypes for detectives, we want to represent different styles of investigation. The classics that jump to mind would be brawler (a detective who gets into scrapes and fights his way out, like Bigby Wolf in The Wolf Among Us), a smooth talker (a detective who uses their wit and charisma to solve crimes, like Columbo), and a sneak (a detective whose specialty is moving about undetected, like some versions of Batman). This gives us some range to let the players express themselves, but all while providing a framework that reinforces the game's design and setting. 

Now we want some skills that can be associated with each archetype. The archetypes won't be something that the players are forced to stick with--they can choose skills from all three archetypes without issue--but they represent pure images of detectives. We might choose to grant a player a bonus for choosing all of an archetype's skills, and we may not, depending on what we want out of the structure. I'm of the mind that it's better to not grant a bonus, as I want my players to choose skills that inform their characters rather than build super-effective characters. So let's go ahead and create four skills for each archetype: 

Brawler:

1. Fists of Fury - Raises unarmed damage from 1d6 to 1d10. 
2. Pile of Bruises - When reduced to 0 hit points, you regain 3 hit points. This can be used once per day. 
3. Sap the Sap - Once per day, you can cleanly knock unconscious one distracted person with a sap.
4. Nerves of Steel - Once per day, you may intimidate someone into sharing what they know. 

Smooth Talker

1. Kind Eyes - Once per day, you may appeal to someone's emotions, convincing them to share what they know. 
2. Fast Talker - Once per day, you may confuse someone, possibly causing them to reveal what they know. 
3. Truce - Once per day, you may talk your way out of being physically attacked. 
4. Con Artist - Once per day, you can visually or audibly impersonate someone. Requires a roll of 1d10, and any roll of 4 or below blows your cover. 

Sneak

1. Right Place, Right Time - Once per day, you can overhear someone discussing important information. 
2. Silent Step - Once per day, you can approach someone without their noticing it. 
3. Shadow Strike - Once per day, you can render someone unconscious if they are unaware of you. 
4. Invisible - Once per day, you can create a distraction and evade anyone who had previously noticed you. 

You'll notice that none of these archetypes or skills are really related to intelligence--that's because I want all detective characters to have a certain intelligence to them, and I don't believe that any of the archetypes disqualify an intelligent character. Further, since none of the skills between archetypes have a monopoly on obtaining information, any character can be vital to uncovering the mystery. As written, these skills allow players to choose their strategy and roleplaying matches in almost any way they wish. I would advise awarding players either 3 or 4 skills at the beginning of a game and then awarding an additional skill each time a player levels up, which in this case will be determined according to progress through the story (as the players discover new secrets, they will be rewarded with new skills). 

So now we have both our archetypes and our skills. We just have a few more details to work out. I mentioned in the "Fists of Fury" skill that unarmed damage begins at 1d6 and goes up to 1d10, so let's fill in other weapon information. A melee weapon grants d10 damage, and a firearm grants 1d20 damage. Though it's tempting to add a "to hit" mechanic to combat, I don't really want combat to be the heart of this game, so I would rather simply say that any attack made by a player character or a non-trivial enemy should have a 75% chance of hitting, regardless of other details. We can have our players roll a d20 and opt for 6-20 being successes, or 26-100 on a d100, or 3-8 on a d8--whatever works best for you and inspires the most excitement. I think bigger dice generally equal greater excitement, but again what works for you is what matters most. 

Then we have the issue of hit points, which are mentioned in the "Pile of Bruises" skill. Again, combat isn't our focus, but detectives often end up in precarious situations, and we need to know how much punishment they can take. I intended 3 hit points to be non-neglible but also not huge; we want a firearm to be able to kill someone in one hit and the melee options to be more drawn-out. I think that a set 15 hit points would serve us well; that would be about three strikes from a melee weapon or one accurate shot with a firearm to render someone unconscious or dead. That's about the balance I want; my detectives are not meant to be running around killing people, but solving crimes, so quick and deadly combat works pretty well, as it will discourage players from spending too much time fighting. 

You may notice that most of these skills are not dice roll-based; rather, they grant the players daily abilities to act in special ways. This means that most of the game is based on strategy rather than luck, which is ideal for a mystery game. Generally speaking, storytelling- and roleplaying-focused games benefit from less randomization, and so I have opted for less dice rolls. But if you're designing a system that is chaotic or disorienting, lots of rolls should be factored into your system. 

This is enough of a framework to playtest. When playtesting, watch for which abilities seem to tilt the game away from where you want it to go, and pay extra special attention to the things your players get excited about. After playtesting, revise your system with your findings in mind; curtail the effects of overpowered abilities and expand on the things your players enjoy the most. But don't lose sight of why you designed the game this way in the first place--you want to keep the spirit you were aiming for alive throughout any revisions unless it doesn't serve you anymore. 

All you would really need now to run a game of Truths for Sleuths would be a story. You could turn to my guide for writing a mystery campaign, or you could use the following sample story, which illustrates how Truths for Sleuths might actually run. Let's pick something that suits our setting (1970s California). I think GMs should go where their inspiration guides them, and my inspiration reminds me that tarot cards (a great passion of mine) were of great popularity in California in the '70s. So this mystery will be a mystical one revolving around tracking down a deck of fabled tarot cards which were stolen from a medium. Now, as the players investigate the missing deck, they will meet a variety of colorful characters from the mystical reaches of California: the sniveling assistant to a mystic who dreams of one day being a master mystic themself, the retired detective who has reinvented themself as a palm reader, the eccentric millionaire who pays handsomely for the advice of the mystic. The deck will seem out of reach, always changing hands before the players can locate it. And as they investigate the mystical community, strange things begin to happen, things which suggest the mystics know more than they're letting on. 

So we started from the framework of "what do we want our game to accomplish?" and now, just a few pages later, we have a full TRPG system and notes for a campaign. It's really isn't too daunting if you take it a step at a time. Just remember to keep asking the question, "how do I create the experience for players that I'm imagining?" And don't be discouraged if your ideas come slowly or if playtesting reveals you need to return to the drawing board. This is just part of the process, and the more you work at it, the better your system will become for both you and your players. Good luck, and have fun!

That's all for now. Coming soon: how to roleplay learning new skills and abilities, descriptions of temples in D&D, and details about agriculture in the gameworld. Until next time, happy gaming!

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