Grinmar
Grinmar is a paid digital RPG engine by GrayWolfOne21, sold via itch.io, that converts a large language model into a deterministic, zero-hallucination game master for solo tabletop roleplaying. It is distributed as downloadable text files and must be pasted into an AI chat interface such as ChatGPT, Claude, Grok, or a local offline model. The purchase includes the full Grinmar Core Edition, the hardcore Grinmar Monolith Edition, and The World of Grinmar: A Survival Dossier. The ruleset is explicitly designed to eliminate the typical text-adventure safety net. It gives the AI a rigid framework with no invented loot, no miraculous exits, and no plot armor. Character outcomes are resolved through the S.I.I.N.S. Matrix (Strength, Intuition, Intellect, Nimbleness, and Social), a deterministic three-tier action gate, and an Attrition Engine that tracks physical degradation. Inventory is limited to five slots, and spent or consumed items are permanently removed. The Core Edition provides the full solo tabletop campaign ruleset, including sensory exploration, NPC psychology, hidden faction motivations, urban downtime in safe zones, and a procedural eldritch crafting system. The Monolith Edition is a stripped-down iron-man system designed for highly focused tacticians: the AI must output a hard mathematical check at the start of every turn and operate under strict word limits to avoid fluff. It also includes diegetic reality fractures that require the player to continuously verify inventory and ledger accuracy. The included World & Faction Dossier is a lore gazetteer describing six shattered continents, physical rules of survival, and the major ideological factions of the setting, such as the Iron-Priests and the Cult of the Molt. Because the product is a ruleset rather than executable software, users must bring their own LLM interface to play.
- Category
- Analytics
- Pricing
- Paid
Problem solved
Grinmar solves the common problem of text-based AI roleplay being overly permissive and prone to hallucinations. It constrains the LLM with a deterministic ruleset that enforces stats, inventory limits, environmental difficulty checks, permanent consequences, and strict procedural rewards. This makes the AI act as an impartial game master that never fudges the dice or creates unearned escapes.
Use cases
- Solo dark-fantasy tabletop roleplaying with an AI game master
- Hardcore iron-man RPG campaigns with permanent consequences
- Prompt engineering to enforce deterministic, rule-bound LLM outputs
- Building structured text adventures with strict inventory and stat tracking
- Using ChatGPT, Claude, Grok, or local models as impartial TTRPG referees
- Exploring an original dark-fantasy world with factions and survival lore
- Developing procedural affix loot and eldritch crafting systems in roleplay
- Running narrative sessions where every check has mathematical outcomes
Audience
- Hobbyists
- Developers
Pros
- Deterministic and zero-hallucination game master rules
- Includes three useful parts: Core, Monolith, and World Dossier
- Strict inventory and stat mechanics create meaningful tension
- Works with ChatGPT, Claude, Grok, and local offline models
- Inexpensive digital purchase with no recurring subscription
Cons
- Requires a separate AI interface and manual prompt setup
- Not a standalone program or interactive application
- Niche grimdark design may feel too punishing for casual players
- No open source or community-editable version is provided
- Rigid syntax and word limits in Monolith Edition reduce roleplay fluidity
Official website: https://graywolfone21.itch.io/grinmar
Canonical LambdaBase page: https://www.lambdabase.com/tools/grinmar