I started D&D a long time ago when the genre smoothly mixed sci-fi and fantasy. So in my mind's eye, and my long running homebrew campaign, many of the planes from the D&D cosmos that were not "transitive" planes, were merely other worlds orbiting other suns in remote systems.
Magic was prevalent in some areas, and technology ruled in others. Some places were a mixture of both.
Heavens and Hells were merely worlds that were controlled, modified, and ruled by powerful entities (gods?). Minor powers likely had demiplanes adjacent to the world inhabited by their followers.
The cosmic lines of power would shift and change as stars and galaxies orbited in a great pattern. Causing the influence of various stars and planets (such as a fire world, or a divine world) to wax and wane on the campaign. Comets, etc.
So basically now that 5e Spelljammer is out, I am putting into words my "final" revision.
To wit;
The majority of campaign worlds are like our solar system, with vast amounts of airless space between the worlds and planets. Each system is considered a "plane of existence" for purposes of magic and spells.
Area with high magic may resemble the description of Wildspace from the new Spelljamming book, while lower magic areas would more resemble our own solar system. Many systems/planes would likely have a mix of areas.
Once you reach the "edge" of such an area/system you may see the faint shimmering glimmer of the astral boundary. It is a this point you may transition from space/wildspace to the Astral, allowing for travel at higher speeds to other areas or systems. You may also ignore the faint glimmer and continue onward into the darkness of the Void Between the Stars on a long and slow journey to other worlds/systems. (good luck on replenishing your air or avoiding death from old age) (and try to avoid the Great Old Ones)
In a sci-fi setting, astral conduits could be wormholes, and the transition to a higher state of being could be a form of hyperspace that allows faster travel, but less interaction with the actual Astral itself. (Unless you want the hyperspace from Warhammer40K.)
Some of the worlds out there could be as fantastical as you like, say an enormous water/vapor planet that works as a floating ocean, or a ringworld built of enormous trees by ancient elves.
Other "PLANES": The center of my "galaxy" is like the Elemental Chaos, worlds and asteroids and chunks of elemental energy and matter that are close enough together to have a mostly contiguous atmosphere. I put the City of Brass on a fire/lava/rock chunk near the center. Since these "elemental" worlds share an affinity, you can kinda world walk from one to the other, making them seem like an infinite elemental plane.
I use the Border Ethereal as a "Spirit World" and you can leave the border and get to either a shadowy reflection of the adjoining world, or a bright reflection (Faerie). I dump demi plane here also.
I have not figured out what to do with the "Dreamscape" plane, functionally it fits in the astral (thoughts etc) but spirits and dreams work together well, so it (or multiple dreamscapes) could exist in the border ethereal.
Considering dumping the Deep Ethereal. Maybe let the Astral (since thought and will are so important) be the conduit for high magic worlds or low magic worlds as it ebbs and flows. Astral Projection is almost like walking in the Border Ethereal, so maybe the "Ethereal" border is really the first stage/layer of the Astral.
BL:
Space is space, unless highly influenced by magic, then maybe similar to Wildspace.
Magic ebbs and flows across the cosmos, carried by the Ethereal (currently) or maybe Astral.
Worlds and Solar systems are treated as planes of existence.
Deep Space is the Void, and you "could" travel through it but probably don’t want to.
Magic was prevalent in some areas, and technology ruled in others. Some places were a mixture of both.
Heavens and Hells were merely worlds that were controlled, modified, and ruled by powerful entities (gods?). Minor powers likely had demiplanes adjacent to the world inhabited by their followers.
The cosmic lines of power would shift and change as stars and galaxies orbited in a great pattern. Causing the influence of various stars and planets (such as a fire world, or a divine world) to wax and wane on the campaign. Comets, etc.
So basically now that 5e Spelljammer is out, I am putting into words my "final" revision.
To wit;
The majority of campaign worlds are like our solar system, with vast amounts of airless space between the worlds and planets. Each system is considered a "plane of existence" for purposes of magic and spells.
Area with high magic may resemble the description of Wildspace from the new Spelljamming book, while lower magic areas would more resemble our own solar system. Many systems/planes would likely have a mix of areas.
Once you reach the "edge" of such an area/system you may see the faint shimmering glimmer of the astral boundary. It is a this point you may transition from space/wildspace to the Astral, allowing for travel at higher speeds to other areas or systems. You may also ignore the faint glimmer and continue onward into the darkness of the Void Between the Stars on a long and slow journey to other worlds/systems. (good luck on replenishing your air or avoiding death from old age) (and try to avoid the Great Old Ones)
In a sci-fi setting, astral conduits could be wormholes, and the transition to a higher state of being could be a form of hyperspace that allows faster travel, but less interaction with the actual Astral itself. (Unless you want the hyperspace from Warhammer40K.)
Some of the worlds out there could be as fantastical as you like, say an enormous water/vapor planet that works as a floating ocean, or a ringworld built of enormous trees by ancient elves.
Other "PLANES": The center of my "galaxy" is like the Elemental Chaos, worlds and asteroids and chunks of elemental energy and matter that are close enough together to have a mostly contiguous atmosphere. I put the City of Brass on a fire/lava/rock chunk near the center. Since these "elemental" worlds share an affinity, you can kinda world walk from one to the other, making them seem like an infinite elemental plane.
I use the Border Ethereal as a "Spirit World" and you can leave the border and get to either a shadowy reflection of the adjoining world, or a bright reflection (Faerie). I dump demi plane here also.
I have not figured out what to do with the "Dreamscape" plane, functionally it fits in the astral (thoughts etc) but spirits and dreams work together well, so it (or multiple dreamscapes) could exist in the border ethereal.
Considering dumping the Deep Ethereal. Maybe let the Astral (since thought and will are so important) be the conduit for high magic worlds or low magic worlds as it ebbs and flows. Astral Projection is almost like walking in the Border Ethereal, so maybe the "Ethereal" border is really the first stage/layer of the Astral.
BL:
Space is space, unless highly influenced by magic, then maybe similar to Wildspace.
Magic ebbs and flows across the cosmos, carried by the Ethereal (currently) or maybe Astral.
Worlds and Solar systems are treated as planes of existence.
Deep Space is the Void, and you "could" travel through it but probably don’t want to.