Overview

Mutabilis is a tabletop roleplaying game about immortal beings of marble whose identities are never set in stone.

Guided by a Game Master, the characters undertake quests that reshape both the world and themselves.

Role and Team

Mutabilis is a 2-3 week long project that I worked on mostly alone. The game design and document design were my work, and the illustration was made by Sdoca08.

Goals

The goal of the project was to create a one-page TTRPG for the One Page RPG Jam 2026, following the jam’s constraints to ensure creativity.

Design

In Mutabilis, identities aren’t defined by numerical stats, but by vows. These don’t just describe what characters are capable of doing, but what they believe themselves to be. They define their convictions, their attachments, and how they perceive themselves. These statements shape their identity and can be challenged by the events of the story.

For example, a character might carry the vow “Whoever hurts my friends must face my blade.” Invoking it when a situation truly matches lets the action succeed beyond expectations, but the vow then fissures: it can be made more precise (“…must face my blade” narrows to only emotional harm), broader (extended to anyone, not just friends), or even flipped into its near-opposite (“…deserves a second chance”), depending on how the table decides the character was changed by the moment. Knowingly acting against a vow instead breaks it outright, erasing it for good.

Process

I researched how one-page RPGs were structured, and gathered inspiration around the jam’s theme. Some game mechanics appeared from brainstorming. Through iteration I stripped the concept down to its core idea / philosophy. I used Obsidian for writing and Canva for document design.

Key Decisions

I had to pin down Mutabilis’s core philosophy to identify which mechanics would translate it best in as few words as possible, while keeping an interesting game loop. For example, erasing a vow used to be its own separate mechanic before I compressed it into the main resolution system. Fragments were also far more complex, offering unique interactions that made them feel closer to vow merchants than to a mirror of a past self. Physical harm to a Mutabilis’s body used to trigger fissures too, but I removed that as well, since it clashed with the game’s philosophy.

Challenges

The one-page constraint really limited what I wanted to do with the project. Usually, one-page RPGs don’t include many examples to illustrate their mechanics, but I judged them necessary to include anyway. This made everything harder to fit onto a single page.

Result

Mutabilis as a one-page TTRPG is now complete, but I started a new version for a full-on TTRPG inspired by the scope of TTRPG books such as Tiny Dungeon.

Reflection

Feedback has shown people found the game’s promise interesting but it didn’t transfer to actual play sessions. Mutabilis’s fantasy isn’t captured strongly enough through the document. A complete TTRPG book will be a nice way to go deeper in what makes Mutabilis unique as a game.