[quote=@Double Capybara]
<Snipped quote>

I am a bit confused here, are you saying these don't exist? Or that they do? (because they really do! We haven't even decided if we are giving those pesky humans the gift of fire yet, so who knows if they will need to steal it.)
[/quote]

I was saying via rhetorical question that such legends do exist and are numerous.

[quote=@Double Capybara]
I think travel won't be as much of a problem as everyone seems to think, it's just that now everyone will devise their own methods and there will be a stronger sense of permanence. 

...
[/quote]

I agree with you completely here- methods of inter-Sphere travel should be fully customisable. My point was that inter-Sphere travel will be so not-a-problem that it is a poor measure of godhood (unlike Mk 2, where only fully fledged gods could perform at-will inter-planar travel). While only a fully fledged god would have the power to create links between the Spheres, I still think that owning a Sphere is a much better milestone for ascension (we can also consider that only the god who owns a Sphere can create links to it, which would make owning a Sphere a prerequisite to making inter-Sphere links).

[quote=@Double Capybara]
Though in all honesty, I don't know how the spheres are situated physically around Galbar. From what Zeph told, I had this impression that by travelling up, you eventually reach a place between worlds.
[/quote]

While the idea of concentric Spheres might work by analogy and is what the mortal philosophers will cook up and the dumbed-down version of cosmology which the gods can tell the mortals, we are not confined to three-dimension or Euclidean geometry. The Sphere named the Cosmos might be accessible by travelling upwards for a few hundred kilometers, and the Underworld could be accessible by tunnelling downwards deep enough, but the Spheres need not occupy the same space-time as Galbar or each other. This Shadowy Alleyway Sphere is accessible from cities across Galbar and requires no apparent vertical travel to get to, although maybe because the original access points were caves it might be a 'lower' Sphere. The Sphere of Fire could have portals both in the sun above and in volcanoes below, which blurs the distinction between 'upper' and 'lower' Spheres.

Additionally, if we want all the Spheres to be connected to Galbar, it doesn't make sense to have a strictly concentric model, because then only two Spheres will be in direct contact with Galbar and the other Spheres have to push through the Spheres in between.

As such, I think that the Spheres shouldn't be physically situated around Galbar at all, at least not in any literal sense of 'physically situated'. Any categorisations of the Spheres (e.g. Upper vs Lower vs Middle, Material vs Spiritual, Order vs Chaos, Good vs Evil, etc.) and associations with Galbaric geometry and geography should be left as emergent phenomena and not baked into the cosmology in any way.