The Ryuutama engine

A while back, I posted about the OD&D game engine. I think that post was helpful to me at the time for understanding how OD&D the game worked at a mechanical level. As I have been reading and enjoying Ryuutama recently, a similar exercise may be informative. This exercise may also provide a good intro to Ryuutama for players familiar with traditional D&D.

There are several broad, generally applicable rules systems: travelers, incentives, journeys, setting, combat, and the ryuujin. I will only focus on the first four of those systems here because they seem most integral to the core engine.


These are the rules for player characters, which Ryuutama calls travelers.

Travelers have three major mechanical underpinnings: classes, type, and ability scores. Class in Ryuutama is more like background in many other games, and provides a set bundle of skills. Example classes are merchant, hunter, and farmer. Travelers get one class at first level and another at fifth level (max level is 10). Type, however, is more like what class means for other games, and can be one of attack, technical, or magic, which map, respectively, to the traditional classes of fighter, thief, and magic-user. There are four ability scores: strength, dexterity, intelligence, and spirit. Ability scores are measured in dice, with d6 seeming to be about average, d8 being one step higher, and so forth. Travelers also have three state variables: hit points, mental points, and condition (a value that fluctuates daily and is sort of like mood).

The major resolution system is the check, which involves rolling two ability dice (sometimes both are the same ability), adding the results, and comparing the sum to a target number (like a difficulty class in D&D terms). For example, accuracy with a blade (basically, rolling to hit, which is based on weapon type) is DEX + STR. Trapping, a hunter skill, uses DEX + INT. Target numbers range from 4 up. The text labels 7 as a little difficult and 12 as very difficult, to provide some orientation.

  • Class: artisan, farmer, healer, hunter, merchant, minstrel, noble
  • Type: attack, technical, magic
  • Ability scores: strength [STR], dexterity [DEX], intelligence [INT], spirit [SPI]

There are a few other details such as favored weapon, carrying capacity, and so forth, but the rules mentioned above are the foundational components. You can check out the full character sheet as well.


Similar to most traditional fantasy games, characters increase in power through gaining levels, and gaining levels requires XP. Concretely, increasing level improves an ability, provides some extra HP or MP, and provides a few other perks depending on which level.

Ryuutama awards an amount of XP each session based on the highest topography target number (more on this in a moment) encountered, the single most powerful monster defeated, and for each benediction (GM-PC power) the referee used.

I like this approach overall because it rewards seeking out challenges and requires minimal bookkeeping. It is generally relatively easy to recall the single most powerful monster and there is no need to track the exact number of orcs or whatever. Further, though the marginal benefit may be small, the game will always reward tackling a more powerful monster or more dangerous environment within a given session.


The journey procedure is a loop that the party engages to move from one fictional place to another. In sequence: condition checks, travel checks, direction check, and finally camping check. The final three checks all use terrain + weather as the target number. Each traveler makes a separate condition and travel check, but the mapper (one traveler designated by the party beforehand) makes a single direction check for the entire party. A single camping check applies to the entire party as well. The travel check is kind of a big deal, because failing it halves the traveler’s HP (which is about as important in Ryuutama combat as it is in traditional D&D combat, though the halving procedure suggests quite a bit more abstraction in Ryuutama compared to what many players assume about HP in D&D).

For each of these journey checks you end up rolling a pair of ability dice (added) versus an objectively determined target number; for example, grasslands = 6, deep forest = 10, strong wind = +1, and hard rain = +3. So, travelers journeying through deep forest in the hard rain will be rolling against a target number of 13.


Travelers journey between places and encounter things. What determines the details of towns, what lies between them, and what challenges relevant to the travelers exist?

Within the setting rules are guidelines for creating the world at a high level, towns, scenarios, and events. These rules are more elastic than other systems and read more like a set of suggestions than a tight set of procedures, though there are worksheets for each (town, world, scenario, event) with prompts, along with the invitation to maybe work through the process collaboratively with players. For example, the town worksheet has spaces for representative building and specialty goods.

Though not explicitly stated procedurally, several aspects of the rules gesture toward the idea of building up the world organically as journeys unfold, while leaving space for some more traditional lonely-fun referee world-building. There is a grid map sheet that players could fill in as travelers journey. The rules suggest an option where all the players design the town for the next session at the end of the current session and place it on the map, indicating what interstitial areas the referee should focus on in preparation.


The ryuujin (GM-PC guardian angel) rules also seem important for running a game of Ryuutama in the expected mode, due to how they support the referee intervening in a limited way to shape the story. However, the ryuujin rules are tied less tightly to the core engine, as far as I can tell, apart from the XP reward for using benedictions as noted above, and so I will end here. See this post for a bit more on the ryuujin rules, if you are curious, and also the ryuujin character sheet.

2 thoughts on “The Ryuutama engine

    1. Brendan Post author


      I think it would make sense for D&D. The main tasks would be to determine what rolls to use in place of the Ryuutama ability checks and if something should substitute for effects on condition score or if those consequences should be dropped.

      Here is a rough draft of an adaptation to something like B/X D&D:

      1. Condition check: skip this
      2. Travel check: use either a d20 STR or DEX check (player choice)
      3. Direction check: d20 WIS check
      4. Camp check: d20 DEX/INT check (choose lowest score)

      Keep outcomes basically the same, but substitute spell recovery for MP recovery and ignore effects on condition score.

      Add possibility of random encounter to travel check outcomes.

      The target numbers could be done the same way as in Ryuutama but would need to be rescaled for d20 if using roll+bonus ability checks. If using roll < = score checks, terrain and weather could apply a penalty.

      If using the relatively harsh effects of failure on HP, I think it would work best to also use something like a death and dismemberment table to emphasize that HP loss is abstract and also so that player characters do not die immediately at zero HP. Search for death and dismemberment table on for some examples of how this might work. Though death and dismemberment sounds harsh and grimdark, the actual effect on play is to provide characters with another safety buffer and one could easily tune the gruesomeness of the results to match desired tone.

      If you wanted to keep something like the effects on the condition score, I might replace condition penalties with a general disadvantage (5E-style) to all d20 rolls until the next camp.


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