The Six Worlds are a tightly knit cluster of Planes that lie on the border between the Centre and the Fringes. Although they were once connected to the great Web of Worlds through the Alus-Deisan Gate, the Six Worlds have been cut-off from the rest of Reshomme since that passage was sealed at the end of the Seventh Age.
Planar travel is common between these six planes, and they support several trans-planar nations. Although each of the planes is very different in terms of climate, biome and celestial bodies, in practice the six function almost as a single, compact-yet-diverse plane. Some planar scholars believe that the Six Worlds (and perhaps the greater Web of Worlds as well) may be disparate Fringe planes that have somehow become entangled over the ages and are now slowly unifying into one massive plane as they drift towards the centre of Reshomme.