One Hero Engine

A Solo Heroic Fantasy RPG

One Hero Engine v0.20 is the current Coherent Playtest Edition of the game. This is the version where the project finally feels like a real playable ruleset instead of a pile of related ideas. The focus is still the same as before: one capable hero, no GM, short sessions, low bookkeeping, and enough structure that I can sit down, ask a question, and start playing without rebuilding the whole system in my head first.

At a glance

Current version: v0.20
Version status: Coherent Playtest Edition
Play style: one hero, no GM, two or three scenes, low bookkeeping
Resolution: universal roll-under d20 tests
Combat: player-facing, two actions per turn, abstract range bands
Character sheet: One Hero Engine v0.20 Character Sheet
Archived draft: One Hero Engine v0.12 Archive

Core design statement

One Hero Engine is a roll-under solo fantasy RPG built for one capable protagonist. It prioritises fast decisions, small encounters, player-facing rolls, and complete adventures in short sessions. I am not trying to make it behave like 5E, trim 5E down, or turn it into a conversion layer for published fantasy material. The point here is to support a specific kind of solo play cleanly and consistently.

What the game is

This version is meant to support a short-session solo fantasy game where one hero can actually get through a complete situation in an evening. The rules are player-facing, the prep is intentionally light, and the encounter scale stays small enough that I do not need to spend more time managing the engine than using it.

What it is not

It is also worth being direct about what this is not. It is not a compatibility layer for 5E, not an O5R retrofit, not a party engine, and not a campaign-management tool. If I want that kind of experience, I would rather use a game already built for it than force this project into a shape it was never meant to hold.

Required materials

You only need a few things to use the current playtest: a d20, 2d6, somewhere to track HP, MP, Tags, Twist, and scene notes, plus either the current character sheet or a plain note page. I wanted the setup cost to stay low enough that starting a session never feels like homework.

Start here

Playtest warning

This is still a playtest edition, so I am treating coherence as more important than breadth. The core procedures are complete enough for short solo sessions, but I have deliberately kept the tested option set narrow. More classes, spells, and subsystems can wait until the current version proves that it actually holds together in play.