The Age of Sorrows is so named for the fall from the First Age, when the mighty Solar Exalted served the gods as righteous kings, before the death-curse of the Primordials drove them mad. In wiping them out, the Dragon-Blooded who now rule may have saved the world, but the wonder of it died with its previous masters. Magic and strange technology still coexist, but it is a lesser thing, and the Dragon-Blooded find themselves struggling: when the Scarlet Empress ascended to the throne, she quelled the Great Contagion and the march of Chaos, but the many deaths changed the shape of the world, and wore holes in small parts of it, Shadowlands where the living and the dead mingle.
Nor did the plague come from nothing--the most infuriated ghosts of the Solar Exalted made deals with the Neverborn, dead Primordials that they themselves killed. In exchange for their names and their assistance in tearing down the whole of the world into nothing, the Neverborn would replace the power that they lost with their deaths, and give them the tools to take their own revenge.
The Age of Sorrows seems to be drawing to a close--the exaltation of new Solar Exalted has begun. The oldest Sidereals are reaching the ends of their lives. According to some sources, the Dragon-Blooded Scarlet Empress, seeking greater power, has (whether intentionally or not) sold herself to demons, and is to be wed to the one of the Yozis — the Primordials who chose imprisonment over death. All of these things together, and the effects thereof, are forcing matters to come to a head. While the first chapter of the Core Rules describes the outcome of the world as bleak, players and Storytellers are encouraged to either put their own spin on it, or break the fate of the world and save it all; aside from that first paragraph, there is nothing to suggest that Creation is doomed--merely headed for a lot of trouble.
The Exalted: The Autochthonians supplement outlines various possibilities for the end of the Age of Sorrows and coins the term Age of Shadows for the presumably darker Third Age of Mankind — a term that deliberately evokes the World of Darkness. Return of the Scarlet Empress presents one possibility for a chronicle ending the Age of sorrows.
Check the main article for a complete Age of Sorrows timeline.