AI RPG Prompt Builder
The gap between "I want to run an RPG inside ChatGPT" and "I have a session that actually works" is almost always the system prompt. Most players skip it entirely, paste a two-sentence placeholder, and then wonder why the AI invents things it shouldn't, loses track of what happened, or never quite feels like a game. A well-structured system prompt is the difference between an AI that thinks it's writing a story and one that knows it's running a campaign for you.
This tool builds that prompt in under a minute. Select your model, genre, tone, focus, and campaign length — the tool assembles a structured, copy-paste-ready system prompt you drop straight into ChatGPT as Custom GPT instructions, a Claude Project's custom instructions, a Gemini Gem, or a Grok Custom Agent. No AI is called. Nothing is sent anywhere. The intelligence is in the template, not in a generation step.
For the best results on Claude, read the Claude RPG guide to learn exactly where to paste these instructions inside a Project. For Gemini, the Gemini RPG guide covers Gem setup — where the 2M-token context window makes this kind of prompt particularly powerful over long campaigns. For Grok, the Grok RPG guide covers Custom Agents and Workspaces — Grok's version of the same persistent container.
Configure your prompt
Long Campaign appends instructions for the AI to produce a periodic memory block you can paste at the start of new sessions. Pairs with the Campaign Memory Tool.
How to Use a Generated Prompt
A generated prompt is a strong starting point, not a ceiling. Paste it into your model of choice and start editing immediately: add your character's name, a specific world premise you've invented, factions, mechanics you want emphasised, or any house rules that matter to you. The prompt gives the AI its operating instructions; everything that makes the campaign yours gets layered on top.
Want to see what the output actually looks like before you build one? Each model has a set of worked, ready-to-paste examples straight from this tool — two complete prompts apiece, plus exactly where they go: Claude RPG prompts (Claude Project), ChatGPT RPG prompts (Custom GPT), Gemini RPG prompts (Gemini Gem), and Grok RPG prompts (Custom Agent + Workspace). For the anatomy behind all of them — the six parts every real RPG prompt needs — see the best RPG prompts guide. Running D&D specifically? The free ChatGPT D&D prompt generator layers a 5e-style ruleset on top of this same tool.
The Claude RPG guide walks through exactly how to set up a Claude Project for a long campaign — including where these instructions go, how to load world documents into Project Knowledge, and what makes Claude particularly well-suited to slow-burn relationship campaigns. The Gemini RPG guide covers the same for Gemini Gems, where the 2M-token context window is a genuine structural advantage for exploration-heavy and long-form play.
If your campaign runs long, the Campaign Memory Tool handles the other side of the problem: tracking characters, plot threads, world facts, and relationships in a structured form, then generating a compression prompt that lets the AI read your full state and return a compact memory block. Between a solid starting prompt and a structured memory approach, coherent AI campaigns past turn 100 are achievable on any platform.
The Arcanum Originals — Aevum Realm Architect, Eirathis Strider, The Chronicler, Star Freighter Drift — solve the system prompt problem from a different angle: they are fully-engineered RPG engines where the prompt, the world bible, and the memory management are all built in from the start. If you want to drop into a complete system rather than build from a template, they are free to download.