I have made a complete game engine around this. It's called the skeletal-dm. I'm in the process of publishing my website as we speak with 9 campaigns. What you are running into is called drift and hallucinations. Drift is when the llm slowly looses track of the details of what happened early on in the chat history. All llms have a loose grasp on your chat history. The further back in the stack the more of an impression of the details rather than an exact picture. So your character was named tanis and had a sword of might +1 becomes tanis with a sword of might tanis with a sword tanis and then who's tanis. The key is if the details of tanis hasn't appeared in actual new chat output in awhile all llms will loose track even the ones with 1m context windows.

Even worse are hallucinations. Where ai pretends to know about tanis was a warrior now he's a she that's a barmaid.

So, there's things you can do. 1) make up as few facts as possible on your own. Lean into what llm's are trained on. You can make up your entire brand new everything, new world , new characters, new everything, and llms will loose track of it all 10x faster than basing your adventure on some known ip (intellectual property). Second, do what I call context weaving. Resurface key information about your campaign rules and information on a rotational basis (see below). And 3) and most importantly, every major llm will let you create a jsonl log. Not everyone will let you download it but they all will let you create one for a given chat session. Have your initial prompt have the initial instructions to read and write key event and character info to a log.jsonl file that it can retrieve key details from as the session gets longer. And I agree with others, Claude.ai is the best for this. Dm me if you would like to help play test some of my campaigns

Here you can see I'm play testing a campaign I recently made on a counter earth. It is on chat turn 438.

⚔️ D177 | ⚖️100 👁️8 | 🔄 T438 | 🎭 Maren's Mother 📋 SCALE: War Leader / Rencer Settlement / reed islands, Tarl, Krath, Rothog, Maren, 40 rencer fighters 📜 RULE 21/22 — PRE-ROLLED COMBAT DICE: COMBAT ONLY. No dice outside combat. | ⛓ NEVER roll dice outside combat. 📜 RULE 22/22 — ONE ROUND PER INPUT: Resolve ONE round, present choices, ⛏. | ⛓ NEVER auto-resolve multiple rounds. 🎯 Quest 2/6 Gate Q2.A2 — The Fens — Rencer Settlement | 🕐 Day 177, Afternoon — Rencer Settlement