Abyss and material planes

[ImperatorK]

What does it take for a normal material plane to become a layer of the Abyss? I know it's not easy, but is it just a big-ass ritual, or is there something more to it?
Once a material plane does become part of the Abyss, what changes occur in it, if any?

 

[Alzrius]

What does it take for a normal material plane to become a layer of the Abyss? Is there something special required to make it possible for a demon lord to add a material plane to Abyss?

The only thing I remember reading in this regard was (if I'm remembering right) in the 2E FR book Faiths & Avatars, under Waukeen's entry, which mentioned that Graz'zt's overall goal in capturing Waukeen was to help him drag the entire Realmspace crystal sphere into the Abyss as a new layer, which he'd claim. I don't think exactly how this could be done was mentioned, though him instituting one of his children as a deity with connections to that sphere was clearly a step in that direction.

Once a material plane does become part of the Abyss, what changes occur in it, if any?

There'd clearly be some changes in the physical nature of the world, but it'd gain the Abyss's planar traits for one thing. Demons would be able to come and go there as they pleased, so there'd be quite a lot of suffering for the mortals there.

 

[SkidAce]

Hard to say in the standard framework of things. Don't think its spelled out, more of a plot device.

In my campaign the "abyss" is a star cluster of worlds, and at the edges is where new worlds get dragged into it.

Of course the center of the abyss is a black hole (of sorts).

 

[ImperatorK]

I'm open to homebrew ideas (I know there's very little official lore about this topic), as long as it doesn't completely ignore or change the official D&D cosmology (pre-4ed).

 

[GX.Sigma]

On the Outer Planes, if enough people believe in a certain philosophy (or are a certain alignment), part of their plane shifts to the plane that matches that philosophy or alignment (this is mentioned in Planescape and actually seen in Torment). As for a piece of the Prime Material Plane, I'd say that would take some pretty powerful magic, since it's more, well, material than the Outer Planes.

It might take a multi-step process: Translate the region into an astral form, which is more mutable. Then translate it into an outer-planar form, which might involve creating, modifying, or waiting for a giant color pool. Then have a bunch of demons move in. The presence of the demons will eventually cause the region to fall into the Abyss.

If you're talking about the entire Prime Material Plane (I'm not familiar with any version of the cosmology where there's more than one), I'd say that would destroy the entire foundation of the multiverse.