Welcome to the EMOVERSE

I'm gonna start my own multiverse. It will be accommodating and include a overworld a underland, a bright kingdom, a dark kingdom, elemental realms, Xor, Psychon, EXOCOM vs the Zone (Mod Special forces vs Sentient Dimension).....

I always like Dormammu dark dimension in dr strange comic that expands into smaller universes.assimilating them, whole universe of broken pocket universes.
"Whats the story?" someone asked. It should shape the setting.

 I'm more into reflecting weird psychological reflective landscapes like moorcock or aldiss but also a bit like medieval art particular their depictions of babylon. Story is wander around interesting places meeting interesting people then murdering them for drinking money then back to the pirate tavern. Eventually you become a aristocrat and your legit colonial goonery becomes totally legit. Repeat till admitted into the military aristocracy repeat till have empire or attack another dimension.
The underland and the overland  are above and below the middle world. The upperlands in the clouds and has forests and many kingdoms hidden from mortals. It connects to the celestial citadel of heaven which has many layers that breach the dome of the sky and the celestial spheres . underland is the deep cavernous wilds and kingdoms below the earth. Then below them, through crust of the of the great arkane sphere are the underworlds, hell's and abyssal shell, dragon pits, remains of previous failed and broken worlds crawling with demons. 

Ok I Have a cheat/work around the hell heaven layer number thing - two contrary historical views of the same data! So people can disagree over what is and isn't heaven and then kill them. Still could do some in between layers for heaven like I did hell. Perhaps a layer of transport infrastructure for tubes and trains and conveyor belts and elevators. A bureaucracy network inside all the structures behind the scenes on every layer. There are several cosmic libraries that teach mortals magic in secret possibly connected to heaven hell and the balance.

The celestial citadel of heaven was built to administer the universe. It is a tall circular steep ziggurat citadel that actually pierced the sky and multiple celestial spheres. Lower heaven layers are sprawling ruined and overgrown now. Once the proletariat gods lived here building the universe but now they live in the world as spirits and lesser nature divinities. They return to them occasionally.

The first layer is walled and moated off from the forest in the cloudlands of the overland. Outside the gate people wait to enter they gate their guide leads them to. The Gatekeeper may decide where they go next. Inside the great garden they look for their allocated stairs or transport to the appropriate level.

Second walled off forested heaven has sacred and holy beasts many of breeds long gone and requiring almost no sustenance save the springs of paradise. They say the gods made many races and monsters here.

Third level is more ruined and inhabited by a higher order of nature spirit and the bright faerie world.

Fourth  is an Arcadian land where sylvan hybrid beings dwell, feasting, playing, drinking and making love often with the visiting gods.

Fifth layer is where stars and beings and lesser gods dwell in the celestial spheres. Some mortals see them in their angelic or deva forms when they visit the sphere of mortals. They have no free will, their destiny and purpose spoken for for all time.

Sixth is more gated. It is a great palace with garden courtyards where the great gods dwell. At night the moon and planetary gods come out to watch the world while the sun king watches by day for evil, darkness and chaos.

Seventh is the land of the old gods and titans who dwelled here in olden times and ruled the cosmos. They are kept here by treaty and curses that limit their influence on the sphere of mortals. The surviving 5% live as peaceful nobles with their chosen living as their serfs in a peaceful rural controlled world.

Arkons are supreme in the eighth layer above (are as demons are to chaos and evil some call them demons of law). Arkons live in the land of light an alien place or pure energy. They always exist and are embedded in all time.

Above that is level nine the Source, a eternal explosion in time of magic power frozen in stasis for eternity. The spark of creation the gods claimed was their source of authority and power. The sun especially uses some of the power every day. Some say the source is ultimate power and could be seized by usurpers but the gods keep it for themselves. Some say to reach the ultimate enlightenment you become part of everything in creation, part of the great unity of Law. Some say this unity is obliteration and the gods and Arcadians are just temptations to stop you attaining final release.

Each layer has a gatehouse and a gate keeper
Its apex is the ruling gods throne room. 
Hell is world of shells,
remnants from the last universe
and left overs from creation
some of the things are incomplete
and leftover beings from the dawn time
or the old universe

hundreds of chaotic fragments
where lawless demon princes
bicker and drunkenly attack worlds at random
each noble with their own madness

Some of the smaller fragments toss and turn through other planes. go to the upper world where it might be destroyed or be used to transport invaders. Mostly demons live in these planes. Sometimes they get mixed up with the cloud islands of the overworld.These fragments and cloud worlds can get around the multiverse and take on properties of other worlds or are remains from building other worlds.

The devils in hell proper keep demons out mostly but a few used as mercenaries or diplomacy. Devils turn chaos against each other using demons to fight extraplanar wars. Devils mostly doing job to persecute mankind and souls. They are licensed and work within the cosmic order. Demons erode the cosmic order maliciously.

One is the porch of hell. A plane with burning lakes, swarms of damned arriving at the gates and getting flogged by devils.  Behind the first wall of hell is a great spiraling pit where each layer is accessed bu gates. A great dragon spawning pit near the active volcano home of Tiamat is here. There are titans and giants and monsters imprisoned under mountains or on some of the broken shell worlds.

Two is a apocalyptic parody of civilization struck by famine, war, plague and death. There are lots of undead and burning ruins and armies at war here.

Three is the underworld a gloomy despairing place where dead live who are sacrificed to and live in some comfort. While better than many underworld dead being forgotten or your lines dying means they will become mere shades or hungry dead ating dung and ash in the ghetto of the underworld.

 Four is a great swamp of foul gloomy monsters and drowned souls and remnants of prehuman damned races and devil dinosaurs.

Five is the great infurno of volcanism and fiery torment

Six is the frozen hell, a great glacier of tears

Seven sea level

Eight jungle hell

Nine great fortress prison citadel

Demiplanes that connect to all the planes of hell
-sewer level
-boiler room
-dungeon dimension
-black library