I like the Abyss. I really do. I enjoyed Planescape and the Blood Wars. One of my first D&D books as a kid in the 80's was the first edition Manual of the Planes. I preordered both Fiendish Codex books, and I have the first one in my lap as I type this.
However, as much as I like the Abyss, I also like alternatives. I like new ideas. I like revisions of classics.
I plan on running Savage Tide in Eberron and I'd like to know how Demogorgon, the Gaping Maw and the Lower Planes of the Great Wheel will adapt to Eberron. I'm afraid the conversion notes are going to be simply use the Shadow Realm to add the Great Wheel to Eberron.
While I don't see anything wrong with using the Shadow Realm, I thought I'd create this thread as a resource for Great Wheel Alternatives. While I'll be concentrating on Eberron ideas, feel free to add other planar ideas here.
My first thought for Eberron is Shavarath. This is the plane of battle. In one single plane you have outsiders of opposed alignments fighting each other in an epic struggle for control. We know very little about Shavarath. Is it infinite? Can it be comprised of finite dimensional spaces, like the Gaping Maw?
There is some information on outsiders in Eberron, and IIRC one of the things that makes them a little different than the ones in the Greyhawk Great Wheel is that they cannot be destroyed. Killing them simply makes them return at a later date. I think the idea behind this is that the planes are a reflection of the "prime material plane" (aka Eberron), rather than a setting where there are multiple primes built from the stuff of the planes.
Another option is Khyber. However, rajahs are typically bound to khyber shards. Perhaps some of the rajahs are loose in the underground of Khyber, but they are also bound to the area by magic similar to the anti-daelkyr fields.
My personal preference is Lamannia. I like the idea of seeing savagry incarnate on this bestial realm, and it seems like most if not all of the monsters described for the Gaping Maw could fit here. It would be nice to see a tie in with lycanthropes; perhaps they have found a realm on the savage end of Lammania and seek its master to aid them in revenge against the Silver Flame. Perhaps there are manifest zones within the planes themselves, with links from Shavarath, Lamannia and Xoriat creating a vile realm for Demogorgon!
These are just a few ideas. I'm leaving for San Francisco (it's 105 in Sac, escaping from the heat this weekend) and won't have internet access for the next few days. (Heathenson, Sebastian and anyone else I forgot can rest easy.)
I'd have to look at my ECS again, but Mabar sounds like it might be a likely fit as well. The idea that the demon princes are allies/hired hands of the rajahs of Khyber is an intriguing one as well that might go over pretty well, if you did some pre-planning.
Is there a possibility that Demogorgon might himself be possessed by a daelkyr spirit, thus explaining his madness? That might be a fun angle.
My idea was to have Demogorgon be a rajah.
(Cheesy name alert) Demog-Orgon looks like a giant kraken, but the two large tentacles end in heads, One a wolf, the other a lion. Bound in an extradimensional space at the bottom of the Dark Sea.
My thoughts are that Big D is either a Raja or a Daelkyr. Until I see the adventure, that is going to remain a bit vague. As to where the Abyss would be in Eberron, Mabar, Krythi or some sunless sea deep in Khyber which is a huge manifest Zone for whatever plane.
I haven't worked too much with the Eberron Cosmology yet. My players are still exploring Khorvaire. In their next adventure, they will be running after one of the PC's AWOL captian from the Last War.