Everyone who travels to the dream realm by onieromancy (rather than actual planar travel) has their stats change:
- Your Str becomes the same as your Cha. Ditto Dex -> Int and Con -> Wis.
- BAB and base saves as a commoner (weak BAB, weak in all saves), as well as hit dice (d4).
- Types change -- intelligent undead, for example, become what they were before being undead.
- Certain abilities are altered (none the party encountered previously).
The Plane of Dreams
http://www.d20srd.org/indexes/planes.htm for reference to terms
The plane of dreams is a plane coexistent with the prime material, as well as its other coexistent planes (the Ethereal and the Shadow). I run all three as "five dimensional" planes that share four with the prime -- the three normal directions, as well as time) -- as well as a fifth being "shallow" and "deep" in its distance from the prime. In the shallow coexistent areas, you can usually see and interact with the prime and back in certain ways. In the deep, the plane takes on more of its own characteristics.
Most travel to the plane of dreams is done through projections like (http://www.d20srd.org/srd/spells/astralProjection.htm). This is how you traveled there previously from Solipsism. However, instead of being a physical clone of yourself, it's a "partial clone" (see the rules above) as your mental attributes can produce. Unlike Astral Projection (and more like ethereal or shadow transporation), when you leave the plane of dreams in a point different than you enter, your physical body "teleports" there immediately.
The shallow plane of dreams is much more highly morphic. This is where people often project themselves when they sleep. The deeper you go in the plane, the harder it becomes to mould the plane according to your wishes -- but the more stable and real these modifications are. This is how Igoriana practiced her craft. The deepest parts of the plane of dreams become almost as if they were their own copy of the prime material, but with these (difficult) morphic qualities.
Some philosophers hypothesize that all three coexistent planes are the same, since they are indeed so similar. They only appear to be different because they loop around and meet back up with the prime at different depths... Indeed, the party has traveled to the deep dream from the deep shadow.