Dragonlance is bad but it's not as bad as Forgotten Realms. I don't know much about Greyhawk but I was under the impression it was a more sword and sorcery style.
I was talking about this the other day, somebody trying to figure out why all the gods and superpowered NPCs of forgotten realms weren't dealing with a world-ending threat by themselves, and it reminded me of my headcanon for Sisyphus from That Which Sleeps (that which will never be released). Now I'm thinking about making that my big villain for my campaign, but I dunno if I'll actually go with it.
There's an arbitrarily large number of Material Planes, and the multiverse is basically a feeding ground for cosmic predators (calling them the Devourers for now). They swim through the astral plane, or embed themselves in worlds like parasites. When a world is ripe, one of the Devourers appears, feeding on the chaos and terror of its arrival and leaving the world barren.
Each world is different, but they have three universal constants. They all have humans, who are special. They all have a Chosen One, who fights his world's Devourer, and they all have Sisyphus, who is cursed with knowing the fate of the world and being unable to stop it.
Humans, playing on the way humans are always the main protagonists in fantasy stories and the other races just kind of sit there, have some secret essence (Humanity, Determination, whatever you want to call it) that gives them their striving, rebellious spirit. Elves and dwarves and even gods are creatures of fate and can't fight against it, while humans tell fate to go fuck itself. The Chosen One is always human. Sisyphus is always human.
Anyway, the Chosen One fights the Devourer and even if he wins it'll just come back in a thousand years. Sisyphus has a plan, to distill the essence of humanity into a New Man, requiring the blood of millions of humans and essentially sacrificing the world, then join the Chosen One's soul to create a supreme being of pure Determination, which can kill the Devourers and end the cycle forever.
But he has to get the Chosen One to go along with destroying the entire world, which always fails. Sometimes the Chosen One kills him, sometimes he kills the Chosen One, but without his consent the world is doomed.
Dunno how I'd do it, or if I'd do it at all, it's pretty weird and awkward since my party has no humans in it at all (minotaur, kobold, dorf, tiefling) but maybe that's the hook. They're all the Chosen One, and they're all non-human, and Sisyphus recognizes this as something unique and redoubles his efforts. I don't see them going along with his plans to kill everybody in the world, but of course the entire theme is bucking against fate so it would be appropriate if Sisyphus's plan wasn't really the only way to save the cosmos.