Ethereal Plane

This plane, along with the Astral Plane, is special because it exists in-between other realms. Both are transitional realms since they only exist in connection to other planes. In a sense, they're the gaps left in between. It touches the prime material plane, as well as the realms of Delirium and Shadow. In the near ethereal realm, one can see everything in the adjacent plane as if through a dense fog. In the same way, Seeing more than a dozen metres through this eerie landscape is hard. One can't interact with the other plane without special abilities to do so but is only limited by it if something has been established on that plane over a long time. Newer walls can be walked through.

In the far ethereal plane, things get weirder. Winding paths lead through disturbing landscapes warped by the ever-present mist. Now and then, a traveller might come across portals to other realms or to the near ethereal of the plane it touches. Navigating is very difficult, and one can get lost for years, centuries, or forever. Or the unweary might end up crossing a portal they don't want.