Welcome to the end of the world.
Well, not the world, as such. Planet Earth's spinning by just as well as it's done for the past few billion years.
And it's not even the end of life on Earth. Sure, there have been some extinctions, but plenty of animals are still kicking, like rabbits, dingos, and dolphins. Hi, dolphins!
Really, calling the mere extinction of 99.9999997% of humanity the end of the world is pretty melodramatic, when you think about it.
So, call it the end of the world as we know it. All civilization was wiped out. Every last human on Earth died. There was nobody left.
Except… Earth isn't the only place humans can be. The Foundation had hide-aways prepared for just this possibility. And so a few thousand humans-researchers, agents, and Class-D personnel were spared the disaster. And after a short time, they came out, and looked at the world that was left.
They were based out of Site-23. A few stragglers from other places, other hide-aways, arrived. But Site-23 had the largest population base of survivors, so it became the new home of mankind. And civilization started anew. With the Foundation in charge.
They knew that a lot of things would of necessity be lost (though it's unlikely they suspected how much). So they worked on making things safe for their descendants. The Class Ds were set to work rebuilding (with various controls devised by Doctor Mann and Doctor Rights), while strike teams led by the likes of Clef, Strelnikov, and Kondraki cleared out new threats. Because this is the SCP-universe, and there are worse things in Australia than dingos. There are monsters, anomalies, and all sorts of unpleasantness. Gradually, they made the land… not safe. It would never be safe, not for many, many years. But safe enough.
But there were costs to be paid. Site 23 was lost when SCP-682 arrived. To trap the creature, they used SCP-184, the Architect, to get it lost deep in endless tunnels, with Agent Strelnikov as bait.
Other researchers went rogue and were driven out. Mann, Kondraki… Others, too. Even the ones who stayed were changed. They used the anomalous items much more readily. What was the point of protecting society, when society was already destroyed? There were fights. Splinter groups.
Eventually, the peoples were split into warring tribes, and more and more knowledge of the past was lost.
That was thousands of years ago. History has faded into legend. The researchers and agents who saved humanity became the common pantheon of the new religion (with variations throughout the land).
Geography is still fairly loose, with few defined places. Most of the continent is much greener than it was in our time. The climate's changed greatly, and there are plains, forests, even rainforest where there was once only desert. Civilization varies greatly from one place to another, ranging from tribes hardly into the bronze age to the city people to the east, who are now firmly into the iron age (with a few having discovered the secret of steel).
The city people live, as their name suggests, in city-states. They war, trade, make alliances, and generally make bothers of themselves. They are more willing than the tribesmen to raid the old ruins for treasures (though it's still considered a very dangerous, cursed enterprise). They've rediscovered the principles of agriculture. They're starting to expand, but there's still a great deal of empty land in the east, meaning that they haven't expanded into other territories much. Yet.
The tribesman live throughout the rest of the continent, and are a varied lot. Some of them are nomadic, while others have permanent settlements. They tend to avoid old ruins and places where strange things live. That said, they're also much more likely to encounter such things. It's not unusual to find a tribesman selling his services to the city people.
There are also people inhabiting the islands around Australia. Humans aren't anywhere near taking their planet back, but they've taken their first steps. Whether or not they succeed….
Oh, and a note on the people. It was a pretty varied lot who survived in Site 23, and they've been living for several thousand years in Australia. Selective pressures have darkened their skin pretty well. There's still some variation, especially in hair and eye color, but almost everyone has darker skin.
Now, there's one other important place. No one, not city people, not tribesmen, will go to the south willingly. That's the home of the Everman. It's patrolled by the walking dead, the New Men, and other monsters he's collected over the years.
The senior staff of the previous times are the gods of the new ones. Some of them did their damnedest to earn the titles, others just did their job, but they're remembered now.
Geyre: The god of smithing and technology, and the chief of the gods. It's said in some tribes that he constructed the old cities, and then destroyed them when they didn't please him. This is especially common among tribesmen who think any city is sinful in old Geyre's eyes.
Drakgin: The god of battle and war. In some places, he's praised as a god for heroes, and they ask him for strength. In others, he's an evil god who brought discord into the world. Some whisper that the dragon Sikayt was his pet, or his steed. Some say he destroyed the old world in a powerful rage.
Kalef: The god of the underworld. The righteous dead will go to him on their final day. He rules a vast empire under ground, on an opal throne. He's also the god of riches. He's known to offer mortals bargains. However, he has a way of twisting them to his own advantage.
Lita: The goddess of nature. She guards the forests and the fields. She's worshipped by hunters, guides through the wilderness, and many of the tribesmen. Her totem is a toothed owl.
Erits, or Old Aggie: The name differs from place to place, but she's always worshipped as a goddess of fertility. Farmers build shrines to her in their fields. In the cities, her temples offer the services of priestesses to lonely men.
Abirt: The god of death. While the righteous dead will go to Kalef, the wicked are Abirt's. When someone dies, they first visit Abirt's realm, where they are judged.
York: The saint of thieves, tricksters and liars. York stole the secret of iron from the gods, planted it among the mortals, and then tricked both to pay him to find the culprit. Some say the end was his doing, a trick gone far wrong.
Starel: Starel is not a god, but the first king. He fought the dragon Sikayt in the Home Ceitu, and both were sealed to protect the world. It is said that one day, when men need him most, he will emerge from the Home Ceitu, unite the people, and bring about a golden age.
There are also numerous local gods. Sometimes they replace gods from the pantheon, sometimes they simply supplement it. Each tribe, each city has its own local version of the pantheon, its own version of events. This is just the most general form of the pantheon.
Wonders and Monsters
These are SCP-Objects, essentially. These are things like the wading pool, the architect, the surgeon crabs. Wonders are the magic items of the Bellerverse. They're relatively rare, but that doesn't mean they're unheard of. Most citystates have a few (locked up by the powerful and wealthy). They can be found in ruins, or in abandoned ceitus. The survivors brought a great number of them to Australia while they still had transportation.
Monsters are, well, monsters. They're SCP creatures. Imagine the Heart of Darkness being encountered by a troop of guardsmen from one of the city-states, or a group of hunters from a tribe. They're dangerous.
Be creative. Ask what SCP might be interesting for them to encounter. And remember that the SCP Foundation hasn't locked away all anomalies. Feel free to invent something, if it fits the story. Hey, maybe you have an SCP idea that you can't make work in an article. Use it here!
Okay, now we're getting into the most important part. This is, basically, a Dying Earth setting in tone. It's an old setting that was once great and prosperous, and was brought low. Unlike most Dying Earth settings, this one's actually recovering, but it still has the same themes of survival, of wonders from the old world intruding on the new. It's sword and sorcery in an old world. Look to Vance's Cugel stories, or Lieber's Fafhrd and the Gray Mouser. It's cynical, but with the promise of exploration, the sense of wonder that comes with a strange world.