Ragnar69 said:
Why does PoL mean equilibrium all across the world? Why not only PoL in the place/time of the campaign? I.e. kingdom ravaged by war, border setting, natural disaster etc.
Heroic adventurers could save a PoL town while the new king strengthens the country as a whole to make it a blob of light. In paragorn tier they have to defend that blob from armies or monsters or demons and epic level could be about unifying different kingdoms to make a very large patch of light. The next campaign then begins in another place of the world that's currently in trouble.
I don't think it's that easy. To me, Points of Light is absence of information deep enough and long enough to make people superstitious about the things that are outside of their sphere of influence and to cause their collective knowledge to shrink down to mostly their own experiences. It's not enough just to be cut off.
For example, if a massive disaster strikes the US, wrecking civilization and isolating me here in Texas, I'm still a modern American. I know about physics and chemistry and psychology and history, and I believe in an objective reality that can be understood with rationality and logic. My isolation isn't automatically going to make me start calling that volcanic fissure the home of the Magma God (although the stress of an apocalypse might, but that's a different story). I may not be able to contact people in Louisiana or Connecticut, or Washington, but I still have a reasonable idea of what people who live there are like, and possibly some knowledge of how they're making out after the apocalypse, depending on how fast communications went down. They're not the alien "other" to me.
And I'm going to teach my kids what I can too. So it'll probably take a few generations before we start getting to that point. I mean, look at the Roman Empire's fall. It took hundreds of years for central authority to disappear altogether, and it took successive waves of barbarian invasion, civil wars, plagues, a ruinous reconquest of Italy by Justinian that bled the country white, and finally the closing off of the Mediterranean to Western trade by an alien culture to bring things to the place they were in the 8th century.
Even if we count from the death of Romulus Augustulus, last Emperor in the West in 476 to the Battle of Tours in 732, a decent candidate for the lowest point in the West, that's a long time for things to get that bad. And in two more generations we've got Charlemagne, and a Western empire again. That's a really short-lived Points of Light situation.
And then we have to consider the fantastic aspects. If Eladrin live 300 years, Elves 200, and Dwarves somewhere longer than Humans, there are going to be potentially a large number of beings around who actually remember when things were a heck of a lot better. If enough of them are around, it's not such a dark age. Even small things like the the Mending cantrip change things significantly - those old manuscripts may be unreadable now, but when things get better enough to start thinking about rediscovering old knowledge, it might be extremely easy old unreadable documents and make them readable again. If nothing else, that speeds up the recovery time.
We can't even throw out the idea of a fallen Empire to make things easier on ourselves if we're playing traditional D&D. Otherwise where did those abandoned keeps, trap-filled tombs, and magical goodies come from? That means the fall is probably long and hard.
So, I guess I'm saying that PoL is either a very specific confluence of circumstances that results in a temporary downturn in civilization (and your campaign story is probably about stopping the free-fall), OR it's a PoL setting in equilibrium, where the forces dragging civilization civilization down are roughly balanced with the forces bringing it up for a good period of time. In the first case, it's difficult to discuss demographics, because that's going to depend heavily on what the original campaign world looked like. In the second, things start to get interesting.