To tell the tale of the River Kingdoms from 4606 AR to 4704 AR is to tell a tale of a river that never changes its course, no matter what storms rage on the land around it. You see, while the rest of Golarion was plunged into the dreadful Age of Lost Omens, the River Kingdoms simply... continued to be themselves, a glorious mess of chaos and freedom.
In 4606 AR, when the god Aroden died, the cosmic shock was felt across the world. In Cheliax, it meant the rise of devils. In Mendev, it meant a war with demons. But in the River Kingdoms, it meant only one thing: the old order was gone, and the strong could now claim what they pleased. The prophets’ silence was no great loss to a people who trusted steel more than fate. The River Kingdoms, which had always been a haven for those who sought to escape tyranny, found themselves with a fresh wave of refugees and a new supply of ambitious souls.
The immediate years following Aroden’s death were, in their own chaotic way, a period of strange opportunity. Established powers like Daggermark and Mivon saw their chance to expand. Daggermark, the City of Daggers, used the confusion to send its assassins and spies to new heights of influence, toppling fledgling lords and manipulating political crises from afar. I imagine a dozen little kings were slain in those years, their kingdoms crumbling before they even truly began.
Meanwhile, Mivon's so-called "emperors" felt their arrogance was justified. With Cheliax now a land of devils, Mivon saw itself as the rightful heir to the legacy of order, though their idea of order was simply to dominate everyone else. They sent their armies out on constant raids, clashing with the free towns and small baronies that stubbornly refused to bow. It was a time of unending, small-scale wars, a perfect backdrop for a young adventurer to make a name for themselves.
Amidst this chaos, the truly remarkable events were often the small ones. In Touvette, the collective of free towns became even more fiercely independent, standing as a bulwark against the tyrannical ambitions of both Mivon and the encroaching Rostland. A simple trade hub like Gralton found itself richer than ever, as river traffic, no longer trusting the old trade routes, found its way to their docks. And the philosophers of Artume simply continued their quiet, intellectual pursuits, debating the nature of the universe as a dozen battles raged just outside their hearing.
As the years marched toward 4704 AR, the world around the River Kingdoms began to settle into its new form. The Mendevian Crusade became a grinding, endless war, and the best-hearted of Golarion's heroes were drawn away to fight it. This left the River Kingdoms to its own devices, a breeding ground for ambitious scoundrels and free-willed heroes who had no interest in a holy war. This was the time when new opportunities presented themselves, such as the chance to forge a new kingdom in the nearby Stolen Lands, a testament to the idea that if a kingdom is not given to you, you may have to carve it out for yourself.
By 4704 AR, the River Kingdoms were a land of settled chaos, where the laws of nature and strength were the only ones that truly mattered. It was a time of great adventure, a land of forgotten ruins, lost treasures, and a thousand different stories waiting to be told.