From the Introduction:
In the beginning, underneath Heaven, there was Nothing. Nothing happened because nothing had to happen; and there was nothing there to stop it, of course. Entropy ruled the void, reining on a throne of illogic.
The Old Ones, finding the world full of nothingness, created Causes. Causes demanded Effect. And thus, the age of Nil became the age of Chaos, the world turning into a primordial ooze of senseless Happenings, an endless howling of insanity. And thus was the universe created.
The Titans, finding the world full of madness, created Justifications. Only Effects could create Causes, but Causes could create Effects. Slowly, the howling void of the age of Chaos became the age of Order, each Titan carving out a Plane to call their Own. And thus were the planes created.
The Sage Kings, finding the world torn asunder into competing kingdom ringed by realms of chaos, sought to unify the Causes - fire and water, air and earth, metal and wood, light and dark, holy and profane, emotion and logic. So did the Sage Kings between them craft the System, which unified the competing Causes into one System of checks and balances, reason and design, merit and necessity, an age of Laws. And thus was the world created.
In crafting the world, just like the forces before them, the Sage Kings sowed their own destruction. In creating the System, they created peoples to enact its laws: human and elf, goblin and troll, orc and fairy, each of the countless races made in the image of their Sage. People who question if the System is not a unification of the causes. merely another Cause whose Effect is simple self-perpetuation, who chafe under an unjust Heaven - but the System, being created by the combined effort of the Sage-Kings, is greater than the Sage-Kings, greater than the Titans, perhaps even greater than the Old Ones themselves. It is the cusp of a new age led by the Folk, where the races created by the Sages take up the mantle of Heaven and direct the System with their own hands.
But even if it is the time for the children of the Sage Kings to take the mantle of Heaven, none know what Age is going to come to pass...