Multiverse Technical explanation

A connected Multiverse

In dungeons and dragons the multiverse behaves in a different way than it does in reality. When connecting multiple fantasy worlds someone would quickly assume it works like there being an earth, at a further distance the sun and somewhere far away that other fantasy planet from another campaign.
In DnD the multiverse doesn't work like that. Or rather not only like that.

The Transitional Planes

At the centre of the each universe lies the physical plane. It's in essentially the Earth. A planet / Universe as you know it. Around these planes lie 2 other planes: The Astral Sea and the Ethereal plane. These 2 planes are transitional planes. They can be used to travel to the elemental planes (inner) or the realms of gods (outer).

Ethereal Plane

A part of the Ethereal plane lays around the physical plane. It is named the "Border Ethereal" and it is essentially a ghost dimension. You'll see that the border ethereal gets mentioned in multiple spells and that even some monsters like phase spiders might reside there. When in the border Ethereal you can see the physical plane but not interact with it. You can even fly through walls and stuff. That's why it's easily described as a ghost dimension.
When you leave the border Ethereal and the physical plane behind you enter the actual Ethereal plane. Most describe it as looking like a giant lava lamp where you move through simply by the power of your mind. Inside this strange dimension you can find vortexes in different shades of colours. Each of these vortexes lets you travel to a different plane of existence. This is why the Ethereal plane is a Transitional plane. From here you can travel to the Inner planes: of Earth, Fire, Water and Air.
I'm not gonna explain more about the inner planes as this article should only cover the basics of planar travel trough the multiverse. In short these planes represent the elements that shape the Physical plane (Arkesh). These planes also lay around the physical plane, having it as centre. The further you travel from the physical plane the wilder the elemental planes become as you travel closer to the Elemental Chaos.

Astral Plane

The astral plane, or commonly named the Astral Sea is a plane of thought. The inner planes resolve around the physical attributes of the Physical plane. Earth, Fire. The things it's made of. The Outer planes are more planes of thought and ideology's. These are the planes where gods reside and where your soul would go after you die.
Traveling through the astral sea.
You can enter the astral sea with both your physical body and your "astral projection" this projection is essentially your soul leaving your body behind. When entering the astral plane through projection you can see a silvery cord attached to your belly button. This cord leads back to your physical body. It can be used to almost instantly pull you back to the physical realm.
Beware however for this cord represents the connection between body and sould. If it's broken your life will end.
The astral sea is described as a silvery pink substande you can swim/fly trough to reach outer planes. Just like the Ethereal plane. (Sorry ok this shit is so complex and I have a hard time understanding it even after reading about it for hours). You move through this plane by thought and can find gates to all 13 (I think) outer planes. Each of the outer planes symbolise each of the possible alignment. Neutral good, Lawfull good, Chaotic good, Chaotic Neutral and so on.

Images like these might help visualise how the planar construct works. In my opinion even with these images they never are able to fully explain the working of the multiverse as it simply isn't easy captured in 2d?

My Multiverse

The chapter above was mostly about the mechanics of the multiverse. It explains the built in lore from DnD. This section is about the lore of my own multiverse.

Origin

Long ago an ancient race named the Creators become so incredibly technologically advanced that the only limit they had to overcome was the experation date of their own soul. The only thing that was still able to get older in their incredibly long lifes.
As a solution for this they decided to built a new universe. A universe where they would live forever. A universe where they would live as gods.
And so they did and when it completed they all "downloaded" themselves to this multiverse and ruled. Their mere thoughts were able to alter planets as easily as pouring water into a cup. You see the multiverse is made up of this incredibly fine code named The Weave. It is this code wizards can access by casting spells. Interacting with the weave through voice, visual or material commands. The creators however could do this with mere thoughts.
However the Creators couldn't rule all as they had created a fast world with far too much to cover and so they created the Gods. A system that would gouvern their planets for them.

Places in my Multiverse

Novum Acrolyn -Hero Planet-

Planes of this setting

Naturalis
The plane of nightmares