> I’ve noticed that bot will mention things from the game that aren’t specifically pointed out in the prompt - ChatGPT clearly has prior knowledge of the Elder Scrolls universe.

I'm working on integrating text generation into OpenMW and I've noticed the same thing. I tell GPT-3.5 that it's playing as "an NPC in The Elder Scrolls III: Morrowind, a character named 'Fargoth'" and it'll start talking about "What brings you to Seyda Neen?" and his ring, despite the fact that I hadn't mentioned either of those things in the prompt.