One of my favourite ideas from Eberron is the Plane of Dreams, Dal Quor.
The idea that sleeping minds reach out to somewhere like a low level form of folk magic, and that it mimics Astral Travel abilities. Just so cool.
I was less pushed by the manifest zones on a material plane, but its certainly an interesting idea.
Why do I bring this up?
Well, I’d like to add a Dreaming Realm to Planescape.
I think it should be fairly straightforward to adapt things. I’m debating how to work it though.
Is the Dreaming it’s own Plane?
Is the Dreaming a realm like the Astral and Ethereal Planes?
Is the Dreaming closer to the Feywild and Shadowfell, with footprints overlapping the Primes?
I’m currently favouring either of the second versions, though I haven’t quite worked it out. Work in progress!