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The Custom design philosophy

Custom and homebrew TTRPG systems are exactly what they sound like: rules designed for one specific game, not to fit an existing family. Some homebrew games riff on OSR principles with custom dice systems. Others take PbtA moves and re-theme them for a new genre. Many more exist in complete isolation — a designer had an idea, built a mechanic no one else has, and ran it.

The common thread is intent. When you design a custom system, you are usually building toward a specific experience that existing systems do not capture. Maybe you want a horror game where your mental stability is the resource tracker. Maybe you want a space opera that uses poker hands as the resolution mechanic. These things exist because someone cared enough to build them.

Custom systems do not have community consensus about how to run them. That is both the freedom and the challenge: you get to define everything, and you have no genre-default to lean on when you are unsure.

Games you can playtest with SagaForge

The custom/homebrew space is enormous and growing. Here are some of the most interesting standalone games that do not fit neatly into existing families:

• Troika! — weird science-fantasy through a portal of your own design. Class-based but each class is fully realized. Designed by Mörk Borg co-creator.
• Lancer — mecha combat with a tactical combat layer (Compendium) and a narrative layer (Noises) that are mechanically decoupled. Unique structure.
• Vaesen — Nordic horror investigation. Uses a locked-die mechanic and Victorian setting to create something with no direct comparison.
• Arboreal — play as spirits inhabiting an ancient forest. Narrative-focused, designed for short arcs and atmospheric play.
• Agon 2e — Greek heroes competing for glory. Fast, episodic, designed for one-shots and convention play.
• Love letters — narrative card game about relationships and stakes. No dice, no grid.
• Aquelarre — Iberian dark fantasy. Medieval Spain, demons, and the Inquisition. Niche and intense.
• A Quiet Year — collaborative world-building. No winner, no conflict resolution — just building a world through prompts.

The custom space is where the weirdest, most interesting design happens.

You do not need a table full of players to find out if your rules work

Homebrew is the hardest thing to playtest because there is no community consensus on how it should run. Your player pool is probably two people — you and maybe a friend — and getting a session scheduled is a logistical puzzle that has nothing to do with whether your rules work.

Custom systems fail in specific ways: a resolution mechanic that sounds elegant but creates absurd results under edge cases, a condition track that nobody can remember, a resource that should matter but never comes up. You will not find these failures by thinking through the rules. You find them by running the rules — and running them when you are the only person available to do it is the whole problem.

SagaForge runs any ruleset you paste. It does not care that you invented your own dice system or that your stat names are unique. It reads what you wrote, plays the game, and tells you where the mechanics broke. 10 actions. 90 seconds. A report you can actually use.