D&D General The cosmology of your homebrew campaign

[Voadam]

I run a mashup homebrew setting with a ton of different elements and pantheons, both fantasy and mythological. I keep a lot of the true nature of the gods and cosmology vague although a lot of the different cosmologies from different settings and mythologies exist as theories in game. I particularly like the 4e world axis cosmology and use it as a base but have used specific elements of the Great Wheel, Golarion, Norse mythology, and World of Darkness spirit realms as planar elements the PCs have encountered directly also.

 

[steeldragons]

My world of Orea follows...mostly....basically....the Great Wheel with a few tweaks and additions. There isn't a ton of planar jumping around...but there need to be places for various critters, challenges, and powerful entities to come from.

The Prime Material Plane includes all of the various planets of what we would call the universe, and all "prime material worlds" from all other physical dimensions of the multiverse.

The "parallel" material planes, that exist "along" the Prime, coexisting at various frequencies include Faerie (the Land of Fae): a material plane "shone through" with the positive energy plane, the Plane of Shadow/Umbral Plane: a material plane "shone through" with the negative energy plane, and the Elemental (and quasi-elemental) planes: planes made of materials composed of the single element energy/type, its various states of matter, and sprinkled with minute traces of other elements.

Along and attached to all Material planes, connecting them to the Positive/Negative Energy planes, and the Ethereal Plane are the Plane of Dreams/the Dreaming, which has a "flipside" (the "Upside Down" we'd probably call it now) Realm of Nightmares - not exactly/entirely its own plane. Fabricated "Demi-planes" (by mortal or other entities) -which require a decently strong connection to the Material realm whence they are originated- tend to exist in this "void" area of energy and ethereal "stuff" (with which to fabricate the demiplane to its creator's specifications).

Coterminous to the Energy/Elemental/Ethereal planes and directly connected at various points within it is "the Spirit World." The happy/kind/helpful/good spirits tend to gravitate more toward the positive energy and fae realms. The not-so-nice/dangerous/evil spirits gravitate toward the more umbral places and negative sides of things.

All material planes are contained within/under an umbrella of the Positive Energy/Light/Radiant plane, and within "above" the inverse "bowl" of the Negative Energy/Entropic/Necrotic plane.

And all of that, including the Energetic planes, are contained within -and saturated through with- the Ethereal. Many homeless spirits, incorporeal undead, several supernatural abilities and those extraplanar creatures which can freely travel to the Material realms are to be found here. Invisibility and several illusion magics involve tapping into/connecting to the Ethereal plane.

Here's where things tend to veer off ye olde canon...

Some sages believe the Spirit World and the Ethereal plane to be the same thing...but this is not technically correct. However, moving through the Spirit World and Ethereal (and beyond) is the Yandr, the River of the Dead. When mortals die on Orea, they find themselves in a shallow skiv upon a mist-shrouded, broad, slow-moving river. How time passes there for the spirit/soul compared to the Material realms is completely inconsistent. When breaks in the mist sometimes allow views of the banks, one can see a lush green, bright realm to one side and a bleak shadow-laden desolate land to the other.

Eventually, at the very last reaches for mortal souls to reach of their own accord, the river forks at the island of the goddess of Death & Fate. It does have a set "in game/world" name that I can't recall atm. The elder goddess Desri knows all of the fates of all mortal souls, when their lives are truly done, and how/what/everything they did in it. It is up to this Judge of Souls to send the skiv down the left fork: tranquil, moving through lush green lands, under beautiful sun- or starlit skies; or the right fork: clearly more rough waters, darker banks, stormy skies, ominous red flashes of lightning in the distance. What she says goes and can not be altered. You're on your way to the Outer planes, for better or worse.

The Outer planes aren't set up in the Great Wheel either. There are no "Twin Paradises" or "Limbo" or "Nine Hells" business.

Good souls go through a series of lands/realms of Good-aligned concentric "circles" (infinite in size) from the NG rolling hills and ever abundant farmlands to the CG idyllic forests to, ultimately, the LG "City" of ultimate goodness, including villas and palaces of the greatest gods of Good.

Evil-aligned, from the desolate murderous battefields of NE to the impenetrable strongholds of LE to the ever-spreading destruction and unending layers within the maelstrom (tenuously contained, in no small part, by the LE realms that keep vigil at its edges) of the CE "Abyss."

Both good and evil Outer planes and the branches of those river forks also further branch out and allow egress to the (again seemingly infinite) Grey Sea, filled with the Isles of Neutrality for neutrals of all leanings to find their ideal final rest, as well as immortal entities and deities of Neutrality to have their own realms, palaces, fortresses, etc...

Sooo...yeah, I think that covers everything.

 

[Blue]

In my current world, the cosmology has grown out of player requests during session 0. You see, our druid wanted something "tangible" that they pull their power from, and suggested that the planet was the dead body of a god, and her skull circled as the moon. I thought if it would impact anything else, saw it wouldn't and approved.

Well, the ... what would you call the entire universe - is that a crystal sphere or is that just a solar system? Anyway, the divine being was pulled into a void universe with no sources of power and killed her, the body left. So the body is both the main source of magic, and a limited resource. The skull is also a plentiful source of magic. The stars on the other hand are nothing. I've even detailed there's no astrology or anything, everything like that centers around the moon. (As a side note, that the moon is a skull is a laughable thought to most people. It looks vaguely skull-like, but it being an actual skull is seen as a child-like belief. The Druids know, though.)

That said, there are other planes with much more plentiful magic. We've been playing for a year and a half and organized religion hasn't really been a factor, there's no pantheon detailed. Part of that is that gods are all very stand-off-ish - mostly because it's just flickers from far away.

We do know from play that there are portals to the Feywild, to some fiendish realm, and that Modrons (and therefore Slaad) exist somewhere as well. But basically the entire universe has a single mote of life and divine power in it, this planet+moon.

 

[cbwjm]

Something I was looking at doing a while back was creating a planar system built on the various cleric domains, that is there would be a plane of life, a plane of death, a plane of nature, etc. Where they intersected, certain other planes would form with the mortal world being the plane where they all intersect. Things like the feywild would be an intersection of something like life, nature, trickery, and arcana. In this setting, clerics were called white wizards (actually, I think I designed an alternate wizard-like class for it) and didn't worship gods so much as focus the energies of a specific plane of existence. Instead of gods, the highest forms of supernatural beings were the various celestial and fiends on their own planes formed by various intersections of the domains of existence. Religions might still exist, perhaps sponsored by a celestial or fiend.

I think I got the idea for this after doing a read of MtG, probably shards of alara, and how the different colours of magic created vastly different worlds when some colours were absent.

 

[AdmundfortGeographer]

Mine superficially resembles @Charlaquin’s in that the setting is in onion-like layers. I’ve taken inspiration from the manga/anime Blame! to construct the world, making it lean to the Dying Earth-end of the spectrum of influence where we’re so far in the future science is indistinguishable from magic. Blame! imagines a transhumanist post-apocalypse megastructure the size of Jupiter in which intelligent life is trapped in the thousands of layers within.

So, start with the central interior hollow world. Inhabitants are the fire-themed elementals, fire giants and devils.

Next layer out, the “underground” unimaginably deep. With deep inspiration from Downcrawl plus Blame! there are caverns the scale of small continents, molded and rearranged by kaiju-scale earth elemental makers. Inhabitants are all the underground species, stone giants, plus opportunity for random weird ones I might want.

The surface layer, the main campaigns exists here, littered with ruins and degraded leftovers from ancient times. Plunder bait.

Above, a sky layer a few thousand miles thick. Think Flash Gordon, Little Price, Dragon Wing…. With major inspiration from Skycrawl. The domain of air elementals, cloud giants, intelligent aerial species.

Above the sky layer, the void of stars filled with asteroid rings filled with human outposts about the main megastructure itself, out beyond the asteroids are synthetic planetoids each the domain of celestial creatures, aberrations, or demon lords and their minions. 4e’s Astral Sea and Spelljammer is big inspiration.

I’m also using something like the idea presented in the DMG of Otherworld to blend Shadowfell and Feywild together. Except I took it more in the direction of Worlds Without Numbers’ idea of Iterums, so there isn’t just a single “Otherworld”.

 

[Orius]

I mostly stick with the Great Wheel. How else am I going to get any use out of my Planescape material?

Mostly I just bolt extra stuff from 3e's MotP onto it. I've got the Ethereal and Plane of Shadow/Shadowfell overlapping the Material Plane one with light and the other with dark tendencies, but neither are particularly good or evil. They serve their typical purposes, with the Ethereal connecting to the Inner Planes and the Shadow theoretical connecting to alternate Material Planes but for me one campaign world is enough.

Inner Planes don't get a lot of change, mostly the old Quasielemental Planes just get reduced to border regions. They never had a a lot of space devoted to them anyway.

Very little change to the Outer Planes. I may do a custom homebrew version of the Outlands but that's it.

The Astral's function of connecting the Material Plane and Outer Planes is replaced by a Spirit World while the Astral Sea surrounds all the planes. There's also a plane of Dreams which is thought to connect the Inner and Outer Planes (Rule of Three!) but it's disputed by sages in Sigil. The Plane of Time exists at the center of all the Planes. The Feywild connects the Outer Planes from the Beastlands to Pandemonium and connects to the Material Plane, Spirit World, and Shadowfell. There's assorted demiplanes, mirror planes and pocket dimensions. And finally there's the Far Realm which is outside the Great Wheel, but with the Lovecraftian feel tuned down a bit in exchange for just general weirdness.

 

[pukunui]

I do like the Norse cosmology and have considered using it before, whether as a full on Norse world campaign or just as a basis for the cosmology. Too many campaigns, too little time.

Same! In fact, I was just thinking about it again last night. I think I’d be inclined to go for more of an MCU approach, though.

I like the idea that the Nine Realms are actually planets rather than different planes of existence and that Yggdrasil is more of a wormhole-like structure than an actual tree.

It’s a bit sci-fi, I know, but the inhabitants of the Realms wouldn’t necessarily know that.


I also really like the super-simple cosmology of Thedas, the world of Dragon Age. There’s basically just the natural world and the Fade, the realm of spirits. They are separated by something called the Veil.

The spirits of all living beings except dwarves go to the Fade during dreams.

There are both good spirits (which embody virtues and concepts like justice) and evil spirits / demons (which embody sinful concepts like pride, desire, rage, sloth, etc).

Powerful spirits can carve out domains in the Fade and make them look however they want.

The Fade kind of stands in for the Ethereal and Astral Planes and maybe also the Shadowfell.


Lately, I’ve also been wanting to build a homebrew world based around dragons. It would be very similar to aspects of Eberron mixed with some ideas from Fizban’s Treasury of Dragons.

So there were three progenitor dragons: Siberys, Khyber, and Erathis. Together they created everything. Khyber betrayed the others and shattered Siberys (the ruby dragon), so Erathis used her own body to imprison Khyber.

Since then, the progenitor dragons’ children have reached greatwyrm status and have become like gods. These include Bahamut and Tiamat.

That’s about as far as I’ve gotten with that setup. I haven’t quite figured out why the dragons would create non-draconic creatures like elves, dwarves, etc. Perhaps they just evolved on their own.

 

[cbwjm]

Lately, I’ve also been wanting to build a homebrew world based around dragons. It would be very similar to aspects of Eberron mixed with some ideas from Fizban’s Treasury of Dragons.

So there were three progenitor dragons: Siberys, Khyber, and Erathis. Together they created everything. Khyber betrayed the others and shattered Siberys (the ruby dragon), so Erathis used her own body to imprison Khyber.

Since then, the progenitor dragons’ children have reached greatwyrm status and have become like gods. These include Bahamut and Tiamat.

That’s about as far as I’ve gotten with that setup. I haven’t quite figured out why the dragons would create non-draconic creatures like elves, dwarves, etc. Perhaps they just evolved on their own.

Perhaps take an idea from Norse mythology and have non-draconic races spawn from the progenitor dragons in a similar way to how dwarves were the maggots in Ymir's body or perhaps the blood that fell in battle gave birth to them.

 

[pukunui]

Perhaps take an idea from Norse mythology and have non-draconic races spawn from the progenitor dragons in a similar way to how dwarves were the maggots in Ymir's body or perhaps the blood that fell in battle gave birth to them.

Hmm. Yes. Like how one origin myth for dragonborn is that they came from the blood of Io.

Perhaps I could merge my ideas. There are lots of things I like about Eberron's setup but I don't want to use everything (otherwise I might as well just use that setting, right?). One thing I'm not so keen to borrow wholesale are Eberron's 13 planes. Perhaps I could use a variation of the Norse Nine Realms instead, with Yggdrasil being the psychic remains of Siberys/Sardior that allows for travel between the realms (so it would be visualised as a dragon rather than a tree).

I'm just about to start my Christmas holidays, so I'll have plenty of time to devote to pondering this over the next few weeks.
(This is all part of my plan to build a homebrew world in which to run a 5e conversion of the Red Hand of Doom.)

 

[Fenris-77]

The cosmology for my most recent setting was a pretty simple civilization/forces of man versus entropy/the wilds. This is a game with no playable races other than human, so I'd have to worry about multiple pantheons.

The Five are the Gods of man (forgive the pronoun), or perhaps more pointedly the gods of human culture. They are Hearth Mother (top of the pantheon) and her husband the Blind Weaver, and their three children the Huntress, the Smith and the Farmer. Each of these Ur-gods have many aspects and variants worshipped at different times and by different people. I didn't set out any of those specifically as that's the design space set out to make the setting replayable and also to allow the players to essentially design their own god if they wanted (there's no mechanical difference, it's currently run with Black Hack). For a given game I'll roll out some aspects that make sense given he characters, theme and whatnot.

The other side of the coin are the gods of the Dark and the deep wild. These I leave less well sketched, again to maintain replayability. The basic list is the gods and goddesses of the Deep Wild, the Sea, Wrath, Corruption and the like. I usually flesh out one or two as needed for a given campaign. Nature gods would mostly fit here, although I usually have aspects of the five that cover some of that same ground. The conflict between two aspects of the same thing, one of the Five and one of the Dark, is a great source of story stuff.

This isn't a good versus evil sort of arrangement at all. The Five represent human culture and the struggle against the encroaching wild and dark. Aspects is where you might get into good and evil if you wanted to go that route. The gods of the Dark aren't evil, although some of them might be seen like that, but are rather the gods of things that are not human, and so probably at least don't care about humans ranging to active antipathy.

 

[Jack Daniel]

My settings' cosmology is analogous to a layered onion, with the "centermost" plane of existence being a static realm of pure Law, and the outermost void a churning sea of Chaotic everything-and-nothing-all-at-once. The planar "layers," from innermost to outermost, are:

The Empyrean Center of All Being
The Platonic Astral Sea
The Inner Etheric Plane (which gradually becomes the Realm of Faerie as one approaches the Material Plane)
The Prime Material Plane (itself a multiverse containing all extant physical universes)
The Outer Etheric Plane (which starts with the Veil of Shadow, which is the realm of the dead, and then gradually fades into…)
The Surface of Limbo
The Void of Chaos

An idea held by some sages — none know whether it's true or not — is that all reality was once one single physical universe, spawned out of the Void by a random quantum fluctuation that became the first Big Bang. Within this universe, some intelligent life-forms evolved and eventually (over countless eons) mastered physics and even transcended mortal limits, only to discover that their vast universe really was nothing more than a tiny, unstable droplet of reality floating in a howling Void of unreality that could perhaps swallow the universe back up in an instant if the proverbial dice ever happened to fall that way. (Think, false vacuum decay.) And so these ascended mortals began to work "outwards" from their fragile reality, creating layer upon layer of stable existence in order to act as a "buffer" between their original universe and the Void — thereby preserving themselves and their original plane of existence. Thus did these transcendent beings, long ago descended from ordinary evolved mortals, become the Creator-Gods of Law.

But as reality became more stable, Chaos began to fight back, and to spontaneously spawn intelligent entities of its own — demons and Chaos Gods, which are essentially Boltzmann Brains (possible because they come from a realm not bound by space, time, or anything vaguely resembling thermodynamics). These entities are wholly dedicated to destruction and entropy, and they encroach constantly on Lawful reality, always trying to help the Void of Chaos swallow existence back up again.

Side note: just for yuks, the planes between the Center and the Void are "shaped" like higher-dimensional platonic solids. The Astral Sea is a hypertetrahedron, the Inner Etheric is a hypercube, the Physical Multiverse is a hyperoctahedron, the Outer Etheric is a hyperdodecahedron, and Limbo is a hypericosahedron — perhaps because some fundamental law of reality required the Gods of Order to build the planes that way in order to keep them stable.

 

[DeviousQuail]

Some of these are really interesting and I will be stealing ideas for the future. In my current cosmology every prime material world is a planet somewhere in the same universe. Look up at the night sky from Homebrew World A and you can potentially see the star that Hombrew World B revolves around. Each of these worlds has some degree of connection to the Ethereal and/or Astral.

The Ethereal is the place where potential starts to find form. It is effectively infinite and home to places like the elemental planes, feywild, shadowfell, demiplanes, etc. There are well-trodden roads, secret paths, and winding trails connecting these realms. Knowing these ways is how most creatures traverse between the prime worlds. One can also head off the ways and into the Deep Ethereal. When done right you can skip all the in between points and move directly to wherever you want within the Ethereal. When done wrong you get ripped into pure potential matter and are lost to the Ethereal entirely.

The Astral is the opposite of the Ethereal. Matter and magic become more static which is why beings here don't age or need to eat. It isn't completely in stasis though so things can be changed. It just requires power and will to do so in contrast to the Ethereals need for power and will to keep things from degrading back into potential. The Astral is shaped like a very crowded solar system. All planets connected to the Astral sit in a large flat disk that revolves around the Astral Star. The more connected a planet is to the Astral the closer their proximity to the star. Most homes for the gods and afterlifes for souls sit in between the planets. It certainly takes on a more space fantasy vibe compared to the Ethereal.

 

[Minigiant]

In my other setting, the comsology is based on Earth's real Cosmos. Also the planes are the gods.

• Solan the Sun and God of Light
• Hegia the 1st Plane of Fire and Goddess of Trickery
• Vegia the 2nd Plane of Fire and Goddess of Love
• Gia the Plane of Earth and the Mother of Life
  • Green the Fey Moon and Goddess of Nature
  • Red the Abyssal Moon and God of Demons
• Megia the Plane of Iron and the Goddess of Battle
  • Diablos the Hell Moon and God of Devils
  • Yama the Hell Moon and Other God of Devils
  • Odin the Vahalla Moon and God of Manlikes
  • Dragon the Dragon Moon and God of Dragons
• Zugia The Plane of Air and the Goddess of Winds
• Sagia The Astral Plane and the Goddess of Time
  • Yellow the Forge Moon and God of the Forge
• Ugia The Heavens and the Goddess of Peace
• Nepia The Plane of Water and the Goddess of Storms
• Hades the Underworld and Goddess of Death
  • Persephone the Elysium and God of Nature
• Centaur the Far Realm of Mutants and Hoofed Star Chaos God of Change
• Minotaur the Far Realm of Freaks and Horned Star Chaos God of War
• The Beast of the Beastlands and Star God of Instinct and Passion
• Hadar the Void and Maw Chaos God of Hunger

 

[Grakarg]

My current homebrew has a pantheon embodied by seven gods. These dieties are the same ones worshipped by all the sentient races with religions, and often have names specific to those cultures and traditions, but are in fact the same divine beings.
The divinities encompass both the positive and negative aspects of their portfolio, so a god of creation is also the god that causes destruction, the god embodying war has militant priests as well as diplomats working for peace. The intent was to have a simple group (seven gods) but have tension and nuance that can lead to conflict for stories. That necromancer cleric you're hunting down? He's part of the same church as the Life Cleric in the party, he just believes he's enacting his god's divine will. How will the cleric in the party react when he learns this?

The Seven in turn are served by a plethora of lesser divine beings who usually champion one aspect of their god and are more active in the world at large. This is the the group of beings that fuel a Warlock's dark pact for example, or might appear in a Paladin's dream asking for aid, etc. Both Celestials and Fiends work to further the aims of the gods. An angel might reward or protect the faithful, and a pit fiend might work to tempt the weak or punish those who've failed the gods. They might even work together for specific aims (like Crowley and Aziraphale from Good Omens) It always creates a bit of a shock for the players when a powerful devil shows up and helps them out.

Demons on the other hand operate outside the auspices of The Seven and create chaos for its own sake or have their own goals. They might create cults among the mortal races that all good worshippers of the seven should work to stamp out. This is to set up situations where previous adversaries of players could find common cause and perhaps work together with them when the need aligns.

All in all, its an attempt to have stuff both ways. A simple pantheon for the Players to use to create characters but still allow me as a DM to create whatever adversary or complication I want to have as needed.

Typically for the classes with a religious bent, the Knowledge Religion skill becomes pretty important.

 

[Minigiant]

I forgot the "best" part of my Solgia cosmology.

Since the planes are gods and most of them are single females, if you seduce a single goddess you can create a demiplane-demigod child to place your stronghold on.

And since one is basically Gender Swapped Zeus, high level fighters and CHA casters often have their own demiplane.

 

[glass]

There's lots of different planes. Each element (air, earth, fire, water, magic) has one.

This reminds me, it looks like I missed elemental planes our of my previous post. My original writeup had a single Elemental Chaos-type plane called The Maelstrom a one of the orbiters, but that does not really work so well with the "orbitting planes influence the World" thing that I shamelessly stole from Eberron have going on. But OTOH, how many/which elements exist is a thing that different cultures disagree with on Pelhorin

Which leads me to a question as to how you lot rule on something: I've always allowed the spell Planeshift to take you from one prime material world/setting to another (e.g. Greyhawk to Toril) in the same universe, even though technically you're still on the same plane. Why? Because otherwise there's no spell that can jump you from world to world. Am I alone or unusual in this ruling, or is this how others handle it as well?

Interesting question. I would not allow you to plane shift from Greyhawk to Toril since they are in the same plane (the Prime Material). As written (at least with the PF1 version), you could do it with two castings, but I might consider houseruling that now that I think about it.

Things are slightly more complicated with my own setting, since the World is in a sense a separate plane from the Skies (with the Skies effectively being alternate Prime Materials - or at least part thereof), but in another sense is in all of them. On balance, I would not allow plane shift from Pelhorin to a Sky, but I would from one Sky to another (locally, anyway).

Plane shifting directly from Pelhorin to Acheron in the GW would be possible, but would be more difficult than just casting the spell normally. Depending on the system it might require a feat and/or some kind of check, and it would definitely need a more elaborate focus than the usual tuning fork.

Mine tends to be Great Wheel (although it actually forms a shell around the multiverse, largely protecting it from the Far Realm)

Do you have another plane "opposite" the Outlands to make a complete sphere (or hypersphere I guess)?

 

[Lanefan]

In my current cosmology every prime material world is a planet somewhere in the same universe. Look up at the night sky from Homebrew World A and you can potentially see the star that Hombrew World B revolves around.

This!

 

[DeviousQuail]

This!

I like it for many reasons but mostly because it's simple. The universe is mind bogglingly vast so I'm not going to run out of room for my worlds. I even put my scifi stuff in this cosmology.

 

[Scott Christian]

I use this:

The realms are ethereal. No one can "visit them" They are just floating objects in the solar system that seem to have an unnatural ability to cross paths with the world of Allor. The people of Allor have developed special telescopes to be able to spot and track some of the realms. Others, remain a mystery as to when they touch.

And touching is the problem. The elemental realm caused a hundred-year storm one time when it just seems to stick to Allor. All the realms have created the creatures of Allor; from sirens to giant spiders, from demons to dryads, from efreet to zombies. Some swear adventurers are people touched by the Supernatural realm.

The realms also brought magic to the world. The people of the world only have elemental magic under control. The other magics are either shunned, and therefore not studied, or studied and caused terrible situations. For when the realms come into contact with people, it seems to change them - most of the time in a bad way.

I use this cosmology to explain the creatures of the world. I use it to explain the magic system. I also use it to explain the old religion, still practiced by the dwarves, northfolk and wilders. And lastly, I use it to "possibly" explain a PCs uncanny ability to live, when most normal people would die.

 

[jmartkdr2]

Start with the wheel, but subtract the planes of conflict. I think its enough to have the basic 8 of LN/LG/NG/CG/CN/CE/NE/LE based, then have Ethereal, Astral, Fey, Shadow. I dont have a Positive/Negative planes, but source I guess, like background energy.

I think on top of the Far Realm you also need a Plane of Dream, I dont really understand why thats not more of a thing, but I guess some of its tropes get eaten up in Fey/Shadow Planes.

I go a bit further: I have three-ish sections in the outer planes:

1. The Upper Planes. Most sit 'behind' Mt. Celesita, across the Astral Sea. So you must go past the guardian angels to get to them. They don't really have a map, they're just a bunch of places for good gods and good souls to reside. Reaching them without passing the guards is nearly impossible.

2. The Abyss. Again, not really mappable, just a bunch of layers that may or may not really be on top of each other. All sorts of fiendish things live here: demons (tanarii, mariliths), rakshasa, slaadi, demonic beastfolk, yugoloths, weird undead, night hags... if it's a fiend and not a devil, it's around here somewhere.

3. Acheron and Hell. Hell sits in the middle of the plane of conflict, which is spotted with hives of fiending insects (chasme, xill, et al), and the devils and their infernal beast pets reside in the middle behind a massive wall.

4. Mechanicus is around here somewhere as well, but it's small enough to be overlooked, and there's room for other stuff.

I do use the Blood War, to explain why these entities aren't more involved in the material plane. Most of the fighting happens in the Abyss (demons hate everything, including other demons) and Acheron (demons want it destroyed as well), with occasional assaults on Mt. Celestia. The downside of this setup is it means gods are either rather distant or somehow not the main forces in the outer planes - I'm okay with this but it means clerics need some tweaking.

The inner planes overlap: it's really one big plane, kinda like the Elemental Chaos, but bog sections dominated by one element are pretty common.