Prompt Architecture for a Reliable AI Dungeon Master

How I structured prompts to make an LLM behave like a consistent, rule-following D&D 5e GM and actually stay that way across long sessions. Building an AI Dungeon Master sounds straightforward until you actually try it. Left to its own devices, an LLM will happily let a level-1 fighter dual-wield longswords, cast spells they never learned, and narrate a killing blow before the player has rolled a single die. Fun the first time. Maddening as a recurring loop. The core challenge isn't creativity LLMs are genuinely great at that. The challenge is consistency . D&D 5e has hundreds of interlocking rules, and a solo player with no human GM to correct mistakes will notice fast when the AI forgets that Warlocks recharge spell slots on a short rest, or that a Bard can't swap their Known Spells mid-dungeon. Get caught bending the rules once, and the player trusts nothing. Here's how I tackled it in SoloQuest . Layer 1: The System Prompt as a Rules Contract The foundation is a dense, versioned sy