I was about to launch a thread for a Planar Renovation for Carceri; but before I get into that, I wanted to ask a general question regarding the layout of the plane.
We all know that the plane has six layers and that it is composed of concentric spheres. But the more I reviewed this, the less certain I was of what was really envisioned by the authors.
When the layers are said to be conatined within the spheres of the previous layer, I can see this in one of a couple of ways
1) In the outermost layer, one sees the chain of spheres. Once one enters one of the spheres, he sees the one (and only one) sphere containted within that outer sphere (with another one hidden inside that sphere, etc.)
2) Entering any of the spheres brings you to the shared inner layer with another chain of infintely linked spheres with shared properties (e.g. all blasted with sand).
3) Once one enters one of the spheres, one encounters a unique chain of spheres accessible only from that outer sphere. This continues fractal-like until the 6th layer [This seems the least likely scenario, but it did occur to me]
Depending on how that first question is answered, how is a layer experienced once one gets past the intial layer? (I.e. if you are on the 2nd layer, what does the arrangement look like?)
-Are you standing on the inside radius of the outer sphere looking up at the inner sphere? I.e. imagine yourself standing inside a basketball with a tennis ball (the inner sphere) floating over head
-Are you standing on the outer radius of the inner sphere looking up at the inside of the previous sphere? I.e. imagine yourself standing on the surface of a tennis ball (the inner sphere) that was hovering in the center of a hollow basketball (the outer sphere). Another analogy would be standing on a world looking up at the crystral sphere that contains it
I had always pictured it one way but upon review, I’m flip-flopping on how it should be. Can someone clarify this?
Option two is the correct one. It's more clear in the 1st edition Manual of the Planes than it is in Planescape.
You go through tunnels or whatever in Othrys, and when you come out you're on a smaller orb, and the other orbs are smaller and more distant. You arrive on an orb equivalent to the sphere on the previous layer, but it's the same chain of orbs you'd see if you entered through some other sphere on Othrys. If you'd entered through a different orb, you'd emerge on another orb. The outer layers are invisible and intangible; effectively, they don't exist once you've passed them.
"The barriers between the layers of Tarterus are always located at the lowest points of a particular orb: at the bottoms of chasms or canyons or in the tunnels beneath the surface. The barriers on one orb always lead to the same orb in the other layer, so the various layers of this plane can be pictured as consisting of nested spheres, one within the next. The barriers between the fifth and sixth layer are underwater. If there are any layers beyond the sixth, their barriers are trapped beneath miles of ice." - 1e MotP, page 104.
The whole "nested layers" thing is conceptual, and shouldn't necessarily be taken literally. If you look up from an "inner" layer, you can't see the inside of the previous layer. It doesn't block your view, and if you fly between the orbs you don't run into it. If you want to reach an outer orb, you'll need to find another way back (the book is silent on exactly what your options are, but says most barriers are one-way). In 1st edition, barriers were places that layers overlapped, similar to the overlap of the Ethereal and Material Planes. You could cross from one to another by force of will, making a Wisdom check to do so. Planescape dropped this idea and just connected layers with planar paths and portals, so you can read "barrier" as "portal" if you want. It makes sense that most portals in Carceri would be one-way, and portals out of Carceri would be rarer than portals in.
If you look up in the sky on Othrys, you see the neighboring orbs filling the sky, extremely close to the one you're on (they're 100 miles apart).
If you look up in the sky on Cathrys, the orbs 500 miles apart, which means their diameter is 400 miles smaller. So the neighboring orbs are much smaller in the sky. You can't see Othrys from there; it's invisible and intangible.
In Minethys, the orbs are 5,000 miles apart, and seemingly 4,500 miles smaller in diameter than Cathrys's orbs.
In Colothys, the orbs are a half-million miles apart. It's not clear how big they are, but the MotP says they're about twice the distance between Earth and the Moon, so presumedly they're about the size of the Moon, and look about half the size.
In Porphatys, the orbs are millions of miles apart. Presumedly they look like distant red points of light.
In Agathys, the orbs are so distant you can't see them at all. The 3rd edition MotP claims there's actually only one orb on Agathys, though that seems unnecessarily limiting. The 1st edition MotP made it clear there's more than one, but they're extremely far away.