The Catalyst Engine is an in-progress tabletop RPG engine for creating narrative-focused tabletop roleplaying games that puts characters through fantastical adventures, turning them into heroes.

Interested in creating a tabletop roleplaying game but you aren't sure how to get started building mechanics? The Catalyst Engine might be for you.

Mechanics

The Catalyst Engine uses a dice pool of six-sided dice, you roll all of them at once and create sets of dice with a matching face value. Choose the biggest set and use its strength, the amount of dice in the set, to: succeed, invest towards greater effects, or charge your character's powers for later. But watch out! The GM can also use one of the rolled sets to add consequences and further their own goals.

That's the core mechanic of the system, and all that is needed to get started creating content for your game. The Making Checks More Interesting chapter goes into greater details on how to build on that core mechanic to enable the type of narrative you want to create.

Characters

In a catalyst-powered game, characters are created by choosing a set of 3 narrative lifepaths, which describe where the character comes from, what they were doing becoming a hero, and what made them choose this life.

Choosing a lifepath gives points to invest into approaches, the "abilities" of the character that define how they do things, and special powers. Powers are defined by the game designer and are your chance to go wild creating rules and flavour!

Making it your own

The Catalyst Engine is intended as exactly that, an engine that will power the vehicle for stories that is your game. It's a core set of rules that you can mix-and-match to fit the type of narrative you want to see.

To make the engine your own, you'll need to define a set of base approaches, powers for the characters to wield, and lifepaths to contain them. The engine will power the base dice mechanics, you can focus on the flavour and advanced rules. The book provide many tips and examples to help you get started.

Should I use this?

The Catalyst Engine is in its 7th revision, and has been lightly playtested. I won't lie to you, this is a very early alpha version of these rules and I intend to keep tinkering with them over time. Based on playtesting and feedback, they might even be entirely rewritten! The version you see right now was uploaded in December 2025 and is not intended to be used in official games just yet. Rather, it's a version intended to gather feedbac.

My main objective here is to stop writing this alone and start sharing it to the world, where other perspectives might improve thin unexpected directions. Feedback is more than welcome. Regardless of the shape the game will take, my hope for this game is for this game to fulfil its mssion:"Enable the creation of narrative-first games that feel fantastical".

If you like what you see even at this stage, feel free to get started creating your own game with this base SRD! Please make sure to read the license before you do.

If you do use the engine for your own game, I recommend rewriting the rules in your own words and style. They were purposefully written as very dry and textbook-like to make them easier to understand for designers.