(dnd setting idea I had and couldn't not write an overview for)
"The afterworld is a big place. Well, the word "afterworld" is a misnomer. It's called the Beyond, and it's less one world, more a patchwork of worlds. Gods, powerful fey and fiends, unknowable eldritch beings, and all sorts of extraordinarily powerful entities have stitched together the vacuous reaches of the Beyond with demiplanes of their own making, populated by the souls of mortals who have passed on.
"It's a popular myth among the mortal sort that travel to the Beyond is instant, almost automatic, free from frustration, nuisance or pain. That couldn't be less true. When a mortal dies and its soul becomes untethered from its body, sure, sometimes it will automatically be whisked away to its proper afterlife. Some gods reward their true believers with chartered air-carriages to their private villas in the clouds. People who have made pacts with devils get pressed onto the black prison-ships of the lower planes and are made to swab the deck. But loose souls, souls who are unclaimed by any of the powers that be, get sent…
"to me. Me and my train, the Twilight Express. Any soul, any race, any final resting place. Anyone with a ticket, me and my crew'll take you to where you need to go. But not for free.
"When you mortals finally give up the ghost, death is but an instant, and then you'll find yourself in Nowhere, the City of Horizons. Loud and noisy, filled with the clamor of countless shopkeepers searching for souls to sell to. What are they selling, you ask? Tickets -- tickets to the afterlife. Their own precious little part of the afterlife, that is.
"Some of them will give you a ticket for free. I say don't listen to them -- it's a scam, unless you were really someone in life, and then everyone will be after your soul. Some will offer you a ticket to their afterlife if you promise to serve their god, or entertain their legions of souls, or work in their manor's kitchen, or accomplish some heroic task in one of the countless planes. You need a ticket to ride the train, though, and the merchants in Nowhere know. Picture the gleeful servant of some pit fiend, offering you passage to the Lava Pits of Czsnerzbeogh, if only you'll work for their master for twenty thousand years of eternity… But if they're offering a ticket, take it. Believe me. You don't want to be stuck in Nowhere without a ticket. The most hellish tortures are preferable to the unconscionable horrors the City of Horizons can unveil, horrors that make even me shudder… And you really don't want to be stuck in Nowhere after the train leaves… and it gets dark.
"Once you're on the train, though, watch your back. Regardless of destination, every soul gets the same ride. Scary as some of the particularly damned souls may be, don't panic: it's a really bad idea to cross our security. They're the finest forces in the infinity of the planes, making sure every soul only gets off where their ticket says they can, and keeping out the freeloaders and the riffraff. Out the window you'll be awed by the full grandeur of the Beyond: the breathtaking spires of the Green Palm Palaces, the bleak austerity of the Xulo Nara Lava Oceans, the quixotic unreality of the Thousand Lotus Fields… And between the afterworlds, the expanses of the Great Grey West, where lone fey rangers camp by lone fires, where packs of crest-wolves and fractal-horn deer stampede across the landscape… It'll make you feel alive again. So to speak.
"As soon as you make it to your stop on the Twilight Express, you'll get off, and then you get to enjoy your afterlife, whatever that may be. You might even be allowed to travel around the Beyond and explore other afterlives, or you can stay put and be content with a nice, quiet undeath. But things are always changing in the Beyond. We're always laying down new railways, paving into the west… There are those who wish to escape their assigned afterlife and wreak havoc across the planes… And there are those who wish to conquer the Beyond and the world of the mortal planes, along with those who wish to keep the Beyond ever wild…
"Don't be a stranger, mortal. Be courageous, be cautious, and always watch your back.
- Death
The Renowned Sir R. "Death" Nevermore
Proprietor and Conductor of the Twilight Express