One of the Dimensions for each Plane is always a Mortal Realm, and Mortal realms are echoes, reflections, shadows, or some form of variant of each other. It is a difficult explanation to give more accurately, since the planet could be completely different, with different names for everything and may not even have magic (as it is said is true of Shades). And yet, they are all part of the same cycle and ultimately are the afterlives we often speak of.
Sometimes people from them travel to us, while people from here have sometimes gone to those places, excepting Shades, from which no one has ever returned. In some of them, the Gods live and exist under different names, perhaps with the Old Ones being more powerful or the Powers behaving completely differently.
Each Mortal Realm has an additional challenge in that just as there is the Fairywilde and the Astral and the Ethereal here, they have their own reflections and interact in similar ways with that realm.
So, the equivalents of the Fairywilde are Heaven, Hell, Euthania, Limbo, Eighth, and Pandemonium. The equivalents of the Astral are: Elysium, The Abyss, Quietus, The Dreamscape, Ex, and Nightmare. Finally, the Ethereal Plane equivalents are Whispers, Karma, Purgatory, Silence, The Dread Domain, and Valhalla.
We have some idea of what three of the Mortal Realms look like for their version of Avilon, gained at great risk and cost.
The seven Mortal Realms are: Wyrlde, Yrthe, The Bleak, Shades, Perition, Kismet, The Unknown