Okay, this is a bit rambling, but the idea has been bouncing around in my head for so long I just need to get it out there.

The idea for my setting is this: Unknown to man, the world looked quite differently not too long ago. Magic was quite real and a force to be feared, for it was mostly wielded by the dreaded priest-kings, who worshipped a force known only as the Outer Dark and its minions, the Abominable Godlings. Mankind was enslaved, fodder for the dark hordes and fuel for the spells of the priest-kings and their acolytes.
However, a group of heroes finally managed to wrest the secrets of magic from the priest-kings and, sacrificing thousands of willing hopeless slaves, managed to actually rewrite not only history but reality as well, shunting magic and the Outer Dark away beyond the walls of unreality.
That happened about ten years ago, but nobody knows it. Reality rewrote itself to account for the lack of magic, implanting false memories into every living being.
The rebels are known as great heroes of history, the priest-kings as history's greatest villains, with nobody knowing that they are all very much alive. The priest-kings still hold positions of power, for they shielded themselves from some of the spell's effects, thus allowing them to "translate" their power into the new rules of the world. They are industrial giants, stick market moguls and heads of governments.

However, without their memories, it would mean little. But the Outer Dark would not be bested so easily and it is reaching out again, awakening memories of conquest and bloodshed....and, through cracks in the incomplete retcon of the world, it sneaks in magic and its own horrid creations.
But it cannot empower its minions fully and the more magic enters the world, the more the heroes remember things, remember the stolen spells and powers. It is up to them to stop the rise of the priest-kings and keep the Outer Dark sealed away...

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That's the basic premise. It borrows from KULT, for those who still know it, but should be distinct enough. is that idea workable? I really would hope for some comments on this...is it worth developing into something more and should I come up with my own system for it or use one that already existst?