SPOILERS FOR MYTH: THE FALLEN LORDS AND ITS SEQUELS
About 360 years ago, a great war between the Light and the Dark came to a close, right on schedule. The mantle of the Leveller had fallen upon Balor, formerly the hero Connacht, and his Fallen Lords were poised to wipe out civilization in the known world and usher in the next Dark Age.
But that didn't happen.
Through some miracle, the Legion, led by the last Avatara and King of the Free Cities of the North, Alric, tore victory, bleeding and screaming, from the proverbial jaws of defeat. They cut off Balor's head and threw it into the Great Devoid, destroying him utterly. All of the Fallen Lords were dead or incapacitated, except for Soulblighter, who fled into the wilderness of the East.
The forces of Light won. They weren't supposed to. They had no idea why Destiny had allowed itself to be thwarted.
About 300 years ago, another war began unexpectedly as Soulblighter marshaled the forces of the Dark and took matters into his own hands. This time, the known world was nearly destroyed by Soulblighter's fury, but Alric, now Emperor of the Cath Bruig empire, struck the Fallen Lord down just in time. The scars from Soulblighter's campaign ran deep - the monsterous Myrkridia had returned to the world of the living, and necromancy had spread far and wide - but the Light was ultimately victorious.
Some speculated that the Cycle had been broken, and no Dark Age would ever come again. Others thought the Dark Age had merely been postponed, but welcomed the extension of the Light's dominance. If there was going to be another war with the Dark, it shouldn't happen for another 1,000 years after the death of the Leveller.
Over the next 300 years, an age of peace, progress, and plenty was experienced in the Light's domain. Magic and technology have both advanced and become more widespread. The Emperors, both Alric and his successor, rule justly alongside the Avatara. New lands have been discovered (or rediscovered) across the ocean to the west and across the land to the east. The undead and other monsters have been thinned out. A new war between the Dwarves and Ghols has begun recently, but it seems to be nothing the Legion can't handle.
Times are good. Except...
Things have become strange. The magic that people began to take for granted has changed in unexpected ways, with the most common mages becoming capable of summoning demons no one has seen before, or performing other feats of mass destruction. Strange creatures have been seen in the wilderness. Mystical phenomena occur randomly across the land, often to devastating effect. The Avatara wage a secret cold war against other powerful wizards, and sometimes against each other. The ghols have exploded in numbers. Frightening dreams haunt sensitive people everywhere. Crime is starting to rise. Ships return to shore without their crews. Crypts full of undead are found in unexpected places. The Trow send cryptic messages to the Emperor. More and more people seem to have difficulty keeping track of the passage of time. Stars move in unexpected orbits. New cults have arisen, and although they claim to be ancient and to have existed continuously for time beyond time, they appear nowhere in the historical record.
And deep beneath the spine of the world, a thing that used to be a man flips idly through the pages of the Total Codex and waits for its chance to make the whole world bleed again.