The Mythos RPG System

In Development by jhamilton

Just to get the background stuff out of the way, I’ve been playing, running, and tinkering with TTRPGs since I was a kid. I’ve loved RPGs since I was introduced to Dungeons and Dragons in the late ’80s. I’ve played and run dozens of different systems since then. I’ve hacked even more than I’ve run. 

When the fire of cultivation fantasy stories was lit for me, I wanted to do some of those things at the table….so I started making notes towards that end.  It never really felt like I thought it should, however.  d20 System, FATE, d6 system, and even Cortex were all tried. The closest I got was Cortex. However, I still felt like there was still something not quite right. I need to stop trying to shoe-horn what I wanted to do into someone else’s means of doing things.  I need to just suck it up, draw on my decades of RPG experience, and build exactly what I wanted for this project. 

Looking for inspiration, I recently brought out the collection of notebooks I’ve kept over the years. Things like setting ideas, story concepts, homebrew material for various systems, and ideas to improve the games I run. I don’t think I quite understood how important those notebooks would be for me down the road. It’s been like a puzzle. When I started conceptualizing this new system, I had some missing pieces. I found them in my old writings.

Before I get into more specifics, I just want to stress that I’m not trying to revolutionize the Tabletop RPG space. I’m not trying to make some end-all, be-all system here. This is just me taking my decades of experience in the RPG space along with the list of things I want to see in an RPG  and doing what I can with them.  I’m making the game I want to play. The fact that others are expressing interest in it is beyond my expectation and is just plain awesome.

The Mythos RPG System (MRPG for short) is my take on a system to handle progression/cultivation fantasy games. Below are the primary design tenants I have for this system:

  1. The Players need to be empowered to do cool %^$^&! The mechanics need to reward creatively not stifle it.
  2. The System needs to allow the Sage (aka GM) to plan as little or as much as they would like and run it easily.
  3. It needs to be easy to teach and learn….in addition to being easy to play.
  4. It needs enough crunch to allow for diversity in characters without making playing the game cumbersome.
  5. It needs to be fun.
  6. It needs to use all the funny math dice, including the d20 (I grew up rolling this absurd die, and want to keep using it).

Those are all the things I decided I wanted to have in a system I develop. Now, I have to start that Journey to get there and put in some work.

Here’s a quick overview of what I currently have going with the Mythos RPG System:


  • Character Level is called Cultivation Level. It is also divided into Realms which represent the distinct power level of Cultivators. As you level up, you get significant advantages when you transition to a new Realm, making you exponentially more powerful than the Realm below yours.  This also determines a character’s core Cultivation Base stats.
  • Cultivation Aspects are used to represent the three facets of Cultivation: Spirit, Body, and Mind. Each will grant relevant features as a character level up.
  • Three Pillars: These act as both a narrative resource and determines a lot of a Cultivator’s starting characteristics.
    • Root: This is essentially the source of the character’s power and how they came to become a Cultivator.
    • Heritage: This shows where the character came from.
    • Persona: This is who the character is outside of being a Cultivator.
  • Pursuits are the way for a character to advance. The system uses a more narrative approach to leveling up. Completing Pursuits grant the XP needed to level your character. The choices you make for your Pillars also give you access to Pursuits based on your choices. Your Mantras will also provide thematic Pursuits for you to complete. Adventures are also a source of Pursuits specifically tailored to that narrative. In addition to being the source of XP in the game, Pursuits also help the player tell the Sage what they want to aim for in the game and gives the Sage ideas for the next Adventure.


  • Attributes are the primary source of the Dice Pools used in the System. You add any relevant Attribute dice when you perform a Feat (more on that below).
  • Five Elements take the place of Ability Scores in this game. In SoD they were based on the Five Traditional Chinese elements. They are the core Attribute aside from Cultivation Base and are references throughout the system. They use a system based on the Five Phases to provide Fortune and Misfortune by comparing the Elements used in a conflict.
  • Cultivation Base is the mechanic strength of your Cultivation’s strength.
  • Skills are handled differently than most systems. Skills represent those areas of expertise that a character has mastered. Anyone can attempt the thing, it’s just that someone with the skill gets to add an Attribute dice to a pull when doing so.
  • Mantras are where all the really cool powers come from. Anytime you use the purview of the Mantra you add its attribute Die to the pool.
  • Treasures are the magic items of the system. They’ll grant Attribute Dice as well as new powers and ways to do things.
  • Assets are collectively the allies, titles, reputations, and external things that can assist the character in their adventures.


  • Core or Feat is an important distinction between actions in this game. Core actions are simpler kinds of actions if you they require the dice, then you make an Effect Roll. Feats are the big cinematic cutscene styles actions and they use the Fate Roll.
  • Effect Rolls are the most common roll in the game. You simply choose the most relevant Attribute Die and roll it. The result is the Effect Points (EP) for that action. Whatever your action as you do it and the EP you roll determines how effective it was. Core Actions use Effect Rolls.
  • Fate Rolls are the big cinematic actions that cause ripples in the narrative. This is when you bring out the d20 and the Attribute Dice Pool. You basically roll 1d20 along with the Attribute Die for any relevant Attributes to represent all the character’s abilities at play in that action, then you use the Dice results to construct the final narrative of that action. Most Fate Rolls will consist of you selecting one of the Attribute Die Results to add to the d20 Result to represent your final Result. The other remaining Attribute die results are used for Effects (like an Effect Roll) and to power other Features a character may have.
  • Players makes the Rolls is a feature of this system. The mechanics are built on a Tiered Difficulty system that puts the dice exclusively in the hands of the players. The Sage can use this system to adapt to the narrative at the table fairly easily. Some features will adjust the Tier of Difficulty in favor of the character a bit.
  • Fortune and Misfortune play heavily into the Difficulty System. Much like Advantage/Disadvantage in 5e, they can make things easier or harder for your character. Fortune lowers the Difficulty Tier while Misfortune raises it.


  • Who Goes First is basically the question that the rolling Initiative determines. All the Players, including the Sage (it’s an exception to Players make the Rolls), and the highest roll gets to decide who goes first. Essentially, if you roll the highest you pick either a PC or the Sage to go first. Once that person is done with their actions, they pick who goes next. Simple as that. The players can put together cool sequences of actions if one of them gets it. Once everyone has had an action, you roll Initiative again and do it all over again.
  • Momentum is how you do the cool stuff. Core Actions in Combat generate Momentum. You spend Momentum to perform Feat Actions. Combats can escalate when the Momentum starts to build. Momentum also allows you to perform some cool Teamwork actions as well.
  • Hitting Doesn’t Matter is an important thing for this system. Core Attacks are basically auto hits because you’re rolling for its Effect only. Even Feats are not clear cut succeed or fail. If you succeed you do exactly what you wanted to do, within reason of your Attribute Dice. If you fail, then you still do the thing, it’s just less effective and it doesn’t necessarily go the way you wanted it to. Feats are almost always based on Techniques and Spells, which will include what happens on a “Failure”.
  • Armor Protects means that instead of raising the bar on being able to hit you, Armor lessens the Effect of a hit on you. Same with Resistances of any kind, actually.
  • Hit Points and Wounds are caused by damage Effects. Your Hit Points represent how much damage you can take before suffering a Wound. So if you have 10 HP, you can take up to 10 Damage before it resets to 0 and you take a Wound level. Wound levels can have an adverse effect by causing Misfortune.

There is a lot more to it, of course, but this should at least give an idea of where we’re heading. We’ll expand on this and more in future development posts. Feel free to join us on our Discord server as well! See you in the next post!