So I'm twisting the idea around a little bit after watching The Green Knight twice and having lots of Arthurian/myth-making thoughts which come with being a big medieval poetry fan, I guess. Taking my liberties with the SRD but hey, why not?
The Object for my game is the mythic antagonist in these kinds of stories who basically does not have agency outside of the eventual myths of the Agents (which I'm currently calling Challengers, but we'll see), and all you can do is basically decide whether to deem them worthy or unworthy of the story, striking them down or not.
So it'll be about two things: individual agents and the decay of a fantasy kingdom over time. I'm taking "not having agency" here very broadly as being unable to make choices in a story that don't just contribute to, you know, making a myth out of someone else.