1) There would still be slavery and cannibalism.
Heroic characters would not participate in Slavery or Cannibalism. They'd be the province of the wicked, the cruel, and the desperate. Mul would not be a "Slave Race", specifically. They would just be Mul. Thri-Kreen wouldn't be cannibalistic as a species, and instead often accused of it because of their strange mindset and weird appearance. Similarly, Halflings aren't cannibals, but there are halfling cannibal tribes that are becoming 'living ghouls' just like all other cannibals.
2) It'd be Points of Light.
Small desert encampments of good people trying hard to survive in a terrible world. Good people in terrible situations in various city-states. Yes, the world is largely destroyed, but even the Sorcerer Kings couldn't wipe out -everyone- on the planet.
3) The Sorcerer-Kings would not be working towards Draconic Apotheosis.
They'd have their goals for "Ever More Power!" with various paths to it rather than one for all of them doing the same boring thing.
4) Kalak is dead.
Tyr the Free City would not be devoid of problems. But Kalak would be in the ground having been killed several days before the start of the campaign setting timeline. Yes. Days. Meaning it's still Chaos in Tyr. Wealthy merchants vying for control of the city through brute force being killed in their homes by revolutionaries.
5) Defiling is not the basic nature of Magic, but a specific use.
Defiling isn't how spellcasting works, but is a tempting and constantly available power boost. Withering a 5ft patch of grass adds +4 damage to any spell. Killing a tree adds +30. Things of that nature. HP taken from party members is a straight 1 to 1 damage boost, but reduces your ally's hit points by the same value until restored, or 1hp per long rest.
6) What happened to the World would not be answered.
Leave it to be a question for philosophers. But there would be no knowledge of the Blue Age or whatever. There'd be some legends of the world before the Sorcerer Kings conquered it, but practically nothing explaining -why- or -how-. You don't need to know everything.
7) Borys would be the "Dragon of Athas" as a unique creature.
He would still demand tributes from the other Sorcerer Kings but it wouldn't be 1,000 people from each settlement or whatever. Resources, Wealth, Food, a true Tyrant King above all others, who sometimes finds little encampments in 'his' deserts and wipes them out.
8) Preservers are trying to save the world.
Largely outside of cities, the Preservers are a group of people who are doing all that they can to preserve what remains of the world and restore some measure of what was lost. They have hope. Maybe it'll work. Maybe it won't. But they're trying to find pockets of life and plants and good soil in the world... and collect them. Bring the soil and the seeds and the life together to try and slowly restore the world.
9) It's not just the Tablelands.
The Tablelands are Borys' place. His territory, with the heart of his "Empire" in the Silt Sea. Beyond it are things like the Crimson Wastes and the Stone Jungle, a place the defilers destroyed but the petrified trees didn't collapse like they largely did in the Tablelands. Yes, there are people in the Stone Jungle and the Crimson Wastes. No. They're not more friendly than the people of the Tablelands. They may or may not have Sorcerer Kings of their own. No one knows. Their languages aren't known in the Tablelands.
10) There are still Gods.
Oh, this one would be controversial... but yeah. In addition to the Elementals, there would be gods in the world, yet. But they'd be practically titans and forgotten gods (a5e Monstrous Menagerie). Creatures you could theoretically kill that exist on a mortal level. But they exist and could grant some measure of power to a hundred followers or so... but as the world dies, so too do they. And they are greatly weakened, and occasionally wrathful. They fear the Sorcerer Kings... who have stolen much of their power. And may yet take the last of it. They tend to masquerade as mortals and hide, acting almost exclusively through their agents.
11) The Sorcerer Kings are also Gods, basically.
They're not full power external to human experience god-beings that drift across the cosmos creating things... But they can directly grant power to their servants like a god would. And have more servants than the "Old Gods". Also killing one of the Old Gods in a ritual could be a path to power for, say, Nibenay or one of the others.
12) There would be rain.
Fitful, hot, and unsatisfying. Occasionally toxic. There would still be rain on Athas... but the thirsting sands consume it and drag it away... The Sea of Silt is actually a -sea-. With some water intermingled with the Silt. And Silt Sea Raiders do all they can to filter out another mouthful of greywater from what moisture remains. After rains cross the Silt Sea, there are -days- of ease and leisure for the Silt Sea Raiders... but once the water slips down past the first 20-30 feet of silt, it's practically impossible to get at. Never enough rain to slake the thirsty masses in the City-States... but enough to let the rovers barely survive.
Heroic characters would not participate in Slavery or Cannibalism. They'd be the province of the wicked, the cruel, and the desperate. Mul would not be a "Slave Race", specifically. They would just be Mul. Thri-Kreen wouldn't be cannibalistic as a species, and instead often accused of it because of their strange mindset and weird appearance. Similarly, Halflings aren't cannibals, but there are halfling cannibal tribes that are becoming 'living ghouls' just like all other cannibals.
2) It'd be Points of Light.
Small desert encampments of good people trying hard to survive in a terrible world. Good people in terrible situations in various city-states. Yes, the world is largely destroyed, but even the Sorcerer Kings couldn't wipe out -everyone- on the planet.
3) The Sorcerer-Kings would not be working towards Draconic Apotheosis.
They'd have their goals for "Ever More Power!" with various paths to it rather than one for all of them doing the same boring thing.
4) Kalak is dead.
Tyr the Free City would not be devoid of problems. But Kalak would be in the ground having been killed several days before the start of the campaign setting timeline. Yes. Days. Meaning it's still Chaos in Tyr. Wealthy merchants vying for control of the city through brute force being killed in their homes by revolutionaries.
5) Defiling is not the basic nature of Magic, but a specific use.
Defiling isn't how spellcasting works, but is a tempting and constantly available power boost. Withering a 5ft patch of grass adds +4 damage to any spell. Killing a tree adds +30. Things of that nature. HP taken from party members is a straight 1 to 1 damage boost, but reduces your ally's hit points by the same value until restored, or 1hp per long rest.
6) What happened to the World would not be answered.
Leave it to be a question for philosophers. But there would be no knowledge of the Blue Age or whatever. There'd be some legends of the world before the Sorcerer Kings conquered it, but practically nothing explaining -why- or -how-. You don't need to know everything.
7) Borys would be the "Dragon of Athas" as a unique creature.
He would still demand tributes from the other Sorcerer Kings but it wouldn't be 1,000 people from each settlement or whatever. Resources, Wealth, Food, a true Tyrant King above all others, who sometimes finds little encampments in 'his' deserts and wipes them out.
8) Preservers are trying to save the world.
Largely outside of cities, the Preservers are a group of people who are doing all that they can to preserve what remains of the world and restore some measure of what was lost. They have hope. Maybe it'll work. Maybe it won't. But they're trying to find pockets of life and plants and good soil in the world... and collect them. Bring the soil and the seeds and the life together to try and slowly restore the world.
9) It's not just the Tablelands.
The Tablelands are Borys' place. His territory, with the heart of his "Empire" in the Silt Sea. Beyond it are things like the Crimson Wastes and the Stone Jungle, a place the defilers destroyed but the petrified trees didn't collapse like they largely did in the Tablelands. Yes, there are people in the Stone Jungle and the Crimson Wastes. No. They're not more friendly than the people of the Tablelands. They may or may not have Sorcerer Kings of their own. No one knows. Their languages aren't known in the Tablelands.
10) There are still Gods.
Oh, this one would be controversial... but yeah. In addition to the Elementals, there would be gods in the world, yet. But they'd be practically titans and forgotten gods (a5e Monstrous Menagerie). Creatures you could theoretically kill that exist on a mortal level. But they exist and could grant some measure of power to a hundred followers or so... but as the world dies, so too do they. And they are greatly weakened, and occasionally wrathful. They fear the Sorcerer Kings... who have stolen much of their power. And may yet take the last of it. They tend to masquerade as mortals and hide, acting almost exclusively through their agents.
11) The Sorcerer Kings are also Gods, basically.
They're not full power external to human experience god-beings that drift across the cosmos creating things... But they can directly grant power to their servants like a god would. And have more servants than the "Old Gods". Also killing one of the Old Gods in a ritual could be a path to power for, say, Nibenay or one of the others.
12) There would be rain.
Fitful, hot, and unsatisfying. Occasionally toxic. There would still be rain on Athas... but the thirsting sands consume it and drag it away... The Sea of Silt is actually a -sea-. With some water intermingled with the Silt. And Silt Sea Raiders do all they can to filter out another mouthful of greywater from what moisture remains. After rains cross the Silt Sea, there are -days- of ease and leisure for the Silt Sea Raiders... but once the water slips down past the first 20-30 feet of silt, it's practically impossible to get at. Never enough rain to slake the thirsty masses in the City-States... but enough to let the rovers barely survive.
