I found On Writing and Worldbuilding: Volume I on Writing and World Builby Tim Hickson to be great! Helped me a lot, plus he does YouTube and is informative on there as well
And for those interested in reading more about this (and craft), I recommend this series:
https://www.amazon.com/Writing-Worldbuilding-I-Timothy-Hickson-ebook/dp/B07PNKHDFZ
He touches on this in one of the volumes. The reviews don't lie here - this guy's stuff is great!
For general writing as well as sci-fi / fantasy world building (eg, how empires rise and fall, magic Systems, etc): On Writing and Worldbuilding - Volume I, by Timothy Hickson: https://www.amazon.co.uk/Writing-Worldbuilding-I-Timothy-Hickson-ebook/dp/B07PNKHDFZ
Edit: here's a link to a list with links to other resources I've found on YouTube which, in my experience, have been just as useful as books on writing: https://www.reddit.com/r/writing/comments/n333f1/the_best_writing_resources_ive_found_via_youtube/gwncmk8?utm_medium=android_app&utm_source=share&context=3
It does cover polytheistic religions. Look, I took this from the Amazon page (https://www.amazon.com/Writing-Worldbuilding-I-Timothy-Hickson-ebook/dp/B07PNKHDFZ ):
>Writing advice tends to be full of 'rules' and 'tips' which are either too broad to be helpful or outright wrong. In On Writing and Worldbuilding, we will discuss specific and applicable ideas to consider, from effective methods of delivering exposition and foreshadowing, to how communication, commerce, and control play into the fall of an empire.
>
>ON WRITING
Part I: Prologues
Part II: The First Chapter
Part III: The Exposition Problem
Part IV: Foreshadowing
Part V: Villain Motivation
Part VI: Hero-Villain Relationships
Part VII: Final Battles
Part VIII: The Chosen One
Part IX: Hard Magic Systems
Part X: Soft Magic Systems
Part XI: Magic Systems and Storytelling
>
>ON WORLDBUILDING
Part XII: Polytheistic Religions
Part XIII: Hidden Magical Worlds
Part XIV: How Empires Rise
Part XV: How Empires Work
Part XVI: How Empires Fall
>
>EXCLUSIVE CONTENT
Part XVII: How I Plan a Novel
Dozens of sidenotes and extra thoughts on all these wonderful stories
I missed one - Monster Hunt NYC.
Good luck on whatever you build! And read these worldbuiding books if you haven't already:
https://www.amazon.com/Writing-Worldbuilding-I-Timothy-Hickson-ebook/dp/B07PNKHDFZ
The subreddit /r/worldbuilding may be of interest.
The YouTuber Hello Future Me has some excellent videos on the topic, and later published a book entitled On Writing and World Building (in two volumes, volume 1, volume 2) The first volume is available as an audio book. They're not aimed specifically at world building for RPGs, specifically, but then world building is world building when you get down to it.
The podcast Writing Excuses has a series of episodes on writing for RPGs. Here's an episode from 2008 when they talk Writing for RPGs with Steve Jackson, and then there were a series of episodes on RPG writing in 2001.
Many authors have published discussions of the craft of writing, some of which touch on world building. For example, Steering the Craft by Ursula K. LeGuin, How to Write Science Fiction and Fantasy by Orson Scott Card (which is far better than its title would suggest). I don't have it handy, but I think Asimov wrote some things about writing. Tolkien's essay On Fairy-Stories talks about world-building, although he calls it "subcreation".
There are limits to what you can learn from discussions of writing novels. Planning a game session has some constraints that novel authors do not have -- namely, you're not in control of what the main characters do. It's not a perfect fit. But it's still useful, or so I've found.
In addition to what has already been suggested (and I highly recommend the Eragon series as well), I'd also suggest the Hunger Games and Harry Potter books for fantasy YA. Both will show several common tropes. However, I also think some of the classics would be good. Though it certainly isn't fantasy, Starship Troopers has great worldbuilding. Throw a rock into Star Wars and you are going to find great use of tropes and world building in books and games. Add in some Isaac Asimov as well, especially since he has plenty of short stories to work with that you can go over with him in an afternoon.
If you really want to narrow in though on these things and help him understand them better, I cannot recommend Hello Future Me (Timothy Hickson) enough. Need help understanding dark lords? He has a video for that. The chosen one? Video for that. Mentors? Video for that as well. Need some world building in there? He's got plenty in that too. Empires, hidden magical worlds, dragons, hard and soft worldbuilding and more. He is an invaluable resource for creative writing of any kind. He even has a book on this stuff.
You should check out Tim Hickson on youtube. He has some fascinating well researched videos on world building using examples from popular culture to illustrate points. He has also published a book on world building which is very popular for people looking to create authentic feeling worlds.
This concept is really interesting. Imagine a group devoted to an ideal (eg communism) who would regularly touch an object created by their founder to gain a true sense of understanding about the movement without any sort of bias or alternative interpretation. How would it change things if there was a holy text that conveyed with perfect accuracy the thoughts and experiences of the author witnessing divine acts.
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I love magic systems like this, it’s so subtle yet profound. Brandon Sanderson has a similar system in his “mistborn” novels (which you should totally read). In this world, some people are able to record their thoughts and identity in “metalminds”. In the future, by touching these objects the user is able to recall the memory or moment in time with perfect clarity making them ideal lore-holders and keepers of historical wisdom. In later books, it is revealed that it is possible to use other people’s metalminds, but the narrative hasn’t progressed far enough to investigate this aspect (we are only on book 6 of a planned 12).
To add additional value and motivation, the entire culture and society of this world has been destroyed by a semi-divine all powerful ruler. Only the worldbringers have the true knowledge of what has been lost and they are ruthlessly persecuted. Thes worldbringers with their metalminds travel the world teaching the slave class about the past and their true history.
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This obviously isn’t the same concept as you have outlined, but I would imagine the cultural ramifications of these artifacts would be similar. I’m imagining the act of accessing the artifact would give you a powerful impression of the creator and then some “ghost” impressions left by everyone who has interacted with it? Eg a document that is signed by every person who ever reads it. The signatures are there, but one could still get a true sense of the creator.
Have I got the right idea?