“An overview of a setting with a complete pantheon and cosmology” is correct! Although, you can play with the idea of “complete” since the idea is to make a very small book that suggests a very big world/cosmos. I’ll update the jam to be a little more explicit about this. I may have gotten carried away doing everything in the style of Lord Entropy’s rules lol.
Writing an adventure in the setting of Nobilis is not “officially” the topic of the jam, but if that’s what you’re really excited about, go for it! The spirit of the thing is to make something small and fun inspired by PTFO and Nobilis, and all the other restrictions are mainly just there to breed creativity as they say!