Thinking about what is necessary to introduce new players to a Big Rubble campaign, let’s start with New Pavis.
Now most humans in New Pavis and Pavis County came from Sartar in the last 3 generations or so. I analogize that to any of the Anglo settlements in the Southwest of the US from the perspective of the 1920s. Sure most of them came from the United States east of the Mississippi, but that history had faded. Sure places like Santa Fe, Albuquerque, and San Antonio had centuries of prior history, but that also faded into the background (except for those who were still tied to that history).
So if you are playing an adventurer of Sartarite background in New Pavis, we can cut things down a lot. You don’t need to know your tribal history as that isn’t all that important – heck, the fact that your tribe might have a feud with another tribe is more a story hook than anything else. You just need to know about the Sartar Royal House, the foundation of New Pavis, and that the Lunars conquered Sartar and then New Pavis, and now those places are free.
Same thing playing a Praxian. You need to know the great tribes, that there are a bunch of minor tribes, and that history has always been the same until the Lunar Army defeated the tribes (thanks to Sable betrayal) at Moonbroth. The Praxians were beat until the White Bull united the tribe. A second battle at Moonbroth resulted in a Praxian victory and now New Pavis pays tribute to the White Bull.
In both of these groups nothing needs to be known about the history of the Big Rubble beyond the fact that it exists. The players can learn what they need to know by playing in the setting – the history of the Big Rubble can be part of a mystery they discover and unravel.
Now if I play a Sun Domer, I have a little more local history. We Sun Domers came here centuries ago, at the request of the King of Pavis. We defeated the trolls and the giants and nomads. He gave us rich lands south of Pavis. But the kings died out, Pavis fell to nomads and then trolls, and then our history became tied to New Pavis. We helped Dorastor’s companions see Yelmalio’s pure light and Dorastor even gave us our own enclave in New Pavis because he needed our friendship. A little more information, but not that much more.
Same thing if I’m part of the Ingilli Riverfolk. We riverfolk have been here forever, and always lived off the river. Old Ingilli befriended Dorastor and got rich off the trade with his city.
The only group that has a lot of background is for the less than a third of the city of Old Pavic background. You were raised on stories of the glory years of Lord Pavis, the Arrowstone Dynasty, Jaldon Goldentooth, and the Troll Occupation. That history might be more real to you than the stories of Sartar and the Lunar Conquest – one day Pavis shall be restored but until then you will bore your friends with stories about Iffinbix and Opilli and Balastor and the lot.
In terms of cults, you probably need to know a bit about the Lightbringers, Ernalda, the Nomad Gods, Yelmalio, Pavis, and Zola Fel. Let’s say 13 or 14 cults total. The rest of basically names you should be aware of – Yelm, Red Goddess, Seven Mothers, Kyger Litor, Zorak Zoran, and so on – but not a lot of details are needed.
Now that is a much easier initial information hurdle than Sartar, which in turn is far easier than the Lunar Empire.
Now this downplaying of centuries old history may seem blasphemous to many – especially from British Isles where there is a long continuous history going back a thousand years. But New Pavis was founded only 75 years ago. Most of the settlers came from Dragon Pass and traveled across the hostile plains of Prax to get there. And the history of Old Pavis is not a part of the history of most of the settlers.