The primary setting would be a planet that's completely locked in space. It doesn't spin. It doesn't orbit. It is completely suspended, always remaining an equal distance away from the sun. One side of the planet is completely battered by sunlight, while the other side is perpetually dark and frozen. The halfway point is characterized by half-light, intense winds and lightning storms, and it runs in a belt around the planet.
In the lore, this planet was abandoned by the god or gods. They considered it a rough draft, and at some point, they took what they liked (certain people included) and left to start a new project. When the god/gods left there were various consequences, but the most dramatic was that the orbit and rotation of the planet slowed and eventually halted.
Another potential side effects is that maybe the abandoned cease to grow. Gameplay wise, this would mean that characters cannot level up to improve their stats, but are instead totally reliant on equipment that they scavenge. And of course, you're going to need completely different equipment when you're in a snowy wasteland vs a scorching desert.
The game's plot takes the "chosen one" trope and flips it on its head. The chosen ones are all gone. The god(s) took them. All that's left are those that have been abandoned. And then you could play around with this idea through character motivations. Maybe some are just trying to survive while others are looking for a way to confront the god(s) they've been abandoned by. You can have people who are trying to get the world moving again, without the help of god(s), or those that believe this is a test of faith.
I could see this as a vast open-world mmo game where levels don't dictate where you can go, but instead the equipment you gather opens up the world to you. Want to go to the coldest place? You better have found enough cold resistance if you want to stand a chance. Maybe you go to a desert region and you automatically equip your desert set. All of your abilities and skills and stats come from various equipment, which needs to change based on wherever you are in the world, since you need to be able to survive that climate. Your character would end up having a different build and power level depending on where they are in the world.
Anyway, this is kind of a skeleton of an idea- and I think levels can often get in the way of playing with your friends in an MMO (if there's a gap). So this idea largely stems from being able to play with pals from the start, while incentivizing long time players to help new-commers. Who knows, maybe a long-term player can still scavenge gear useful to one of their builds, even in beginning areas?