Transitive Plane

A transitive plane was a realm of existence that emerged, or was designed, in order to facilitate travel between other planes. There were thought to be three transitive planes: the Astral Plane, the Ethereal Plane, and the River Styx.

The Astral Plane was said to connect all the Outer Planes, the Ethereal all the Inner Planes, and the River Styx to both.