A new series: building a homebrew in Grimoire
Starting a new series. I'm building my homebrew setting Geux from blank campaign to first session, in public, in Grimoire. Here's why and what's coming.
Grimoire was built with running games in mind. It’s as much a repository for your homebrew and story as it is a tracker for the world’s changing state, all on structured data. In this series I’ll be building my own homebrew setting and campaign from initial setup through actually running sessions. All the fun moments, lessons learned, and mistakes made along the way. The point isn’t a tutorial. It’s to show how I use Grimoire in my own workflow, and to illuminate the parts where Grimoire is flexible enough to fit your own settings and scenarios.
My world, briefly
My homebrew setting is called Geux (“Go”). It’s heavily inspired by games like Caves of Qud and RimWorld. I play within the D&D 5e ruleset because it’s easy to homebrew custom mechanics on top of, and I enjoy the bestiary enough to use it where applicable. I write my own creatures when the situation calls for something else. I’ve run one campaign in this world before, but I think I’ll take what I learned and rewrite some canon rather than extend the world we already played through.
When creating my campaign, rather than selecting one of the preset genres I’ll build my own. My system uses D&D 5e as the ruleset, but there are caveats I want written into the genre description, and I want to change the technology level baked into the default Fantasy base.
Vibe-wise, Geux is retro-futurism with fantasy elements. There’s magic. There’s also machinery. The two have a history with each other, and that history shapes basically everything.
Grimoire lets you describe “how prevalent is technology” and “how prevalent is magic” as separate two-axis sliders, which is exactly the lever I need: a far-future tech ceiling at near-mythical prevalence, with isolated communities capable of high magic. That’s the shape of Geux without me writing a single lore note yet.
I’d be lying if I said my own homebrew didn’t influence how the magic and technology dimensions inside Grimoire work, but I think that distinction matters for defining a setting’s extents. If you can think of other similar dimensions that exist in storytelling or TTRPGs and deserve the same kind of axis at campaign creation, reach out.
Grimoire ships with seven base genres now: Fantasy, Sci-Fi, Post-Apocalyptic, Horror, Modern/Urban, Superhero, and Historical. My setting feels sci-fi. My mechanics are fantasy. So which do I pick?
Despite going custom, still Fantasy as the base.
The genre picker decides whether the creature dropdown offers dragon or android, among other things. It decides what entity types are on by default. My monsters come out of the Monster Manual and I want fey and fiend in the dropdown, so Fantasy is the right base. Using the custom homebrew builder I can layer “Sci-Fi” on as a facet rather than the base genre, and still pull in entities like android that show up in my homebrew.
This is the kind of nuance that, in past tools, I had to repeat across a dozen documents and still couldn’t get an AI to respect. In Grimoire, it’s a configuration choice every layer downstream inherits from.
What goes into the Constitution next
Once the campaign exists, the next move is seeding the Constitution: the world foundations graph plus the Campaign Bible. (For the architectural reasoning behind why the Constitution exists at all, see the secret sauce post.)
On day one I’m not trying to write the whole world. I’m thinking about it in the abstract and writing down how the largest concepts, themes, and events connect to define the setting. This is where you set the explicit rules of your world. The AI loads these concepts every session, so it’s grounded in your abstractions and rules before it ever sees an individual entity. For Geux, my foundations will revolve around:
- The founding event that explains why magic and machinery share a world at all.
- Lost-tech salvage, cybernetics, and mutations.
- The central cultural and ideological tension the campaign is going to put pressure on.
- The economic reality of a disconnected feudal system.
- A hostile world and the sparseness of organized civilization.
The Campaign Bible gets one entry first too: tone and meta. Story-focused this time. Where the lines are on content. How sessions are structured.
What’s next
Next post: world foundations nodes for Geux, written out. After that: my workflow for creating the first entities in the database, before inviting my players and running Session 0/1.
If you’re building your own homebrew and want me to show a specific part of the workflow, tell me what you’d want to see.