I do like the Norse cosmology and have considered using it before, whether as a full on Norse world campaign or just as a basis for the cosmology. Too many campaigns, too little time.
Same! In fact, I was just thinking about it again last night. I think I’d be inclined to go for more of an MCU approach, though.
I like the idea that the Nine Realms are actually planets rather than different planes of existence and that Yggdrasil is more of a wormhole-like structure than an actual tree.
It’s a bit sci-fi, I know, but the inhabitants of the Realms wouldn’t necessarily know that.
I also really like the super-simple cosmology of Thedas, the world of Dragon Age. There’s basically just the natural world and the Fade, the realm of spirits. They are separated by something called the Veil.
The spirits of all living beings except dwarves go to the Fade during dreams.
There are both good spirits (which embody virtues and concepts like justice) and evil spirits / demons (which embody sinful concepts like pride, desire, rage, sloth, etc).
Powerful spirits can carve out domains in the Fade and make them look however they want.
The Fade kind of stands in for the Ethereal and Astral Planes and maybe also the Shadowfell.
Lately, I’ve also been wanting to build a homebrew world based around dragons. It would be very similar to aspects of Eberron mixed with some ideas from
Fizban’s Treasury of Dragons.
So there were three progenitor dragons: Siberys, Khyber, and Erathis. Together they created everything. Khyber betrayed the others and shattered Siberys (the ruby dragon), so Erathis used her own body to imprison Khyber.
Since then, the progenitor dragons’ children have reached greatwyrm status and have become like gods. These include Bahamut and Tiamat.
That’s about as far as I’ve gotten with that setup. I haven’t quite figured out why the dragons would create non-draconic creatures like elves, dwarves, etc. Perhaps they just evolved on their own.