The Cataclysm

We who remember are as cursed as the very world we live upon. Day by day there are fewer of us, but the memory never fades. The land is still torn asunder, empires destroyed and so much knowledge buried. Worst of all, the gods have abandoned us. Did they despise us so much that they caused the Cataclysm as their final goodbye? Or did we offend them by bringing about our own pain, that they felt abandoned. I do not know. In time all memories of Cadash before the Cataclysm will be reduced to dreams. For we now live in a nightmare of Chaos.

- Abbas Adra, Leader of the Steluna Elves

Summary

The exact date of the event known as the cataclysm is not known. Ancient elves do remember the event, and based on that we can estimate it occurred around 600 years ago. What is clear from the evidence of ruins and the Rift is that some powerful magical destruction erupted in the ancient capital city of Tyr, the center of the Tyrian Empire. The entire city and surrounding lands were bombarded by arcane energies and then sucked into the very ground. The Rift marks the location of the epicenter, but the rest of Cadash  suffered as well.
Shockwaves of power covered the planet. Some caused tremors that shook cities to rubble, or the ground to sink below them. Mountains formed where none where before, and some areas were blasted into a wasteland. Even those living on islands in the The Sea of Dread were impacted as tidal waves flooded and sunk their homes and settlements.
There are stories of magic being disrupted and going wild. Others claim that monsters spilled out of the Rift and soon ran amok among the survivors. In any case, the amount of undead seemed to greatly increase in the wake of the cataclysm, especially round the Rift.
The disruption of magic is believed to contributed to the desire of the survivors to restrict magical powers and knowledge. But some claim that the gods Yeno in particular have removed their favor form Cadash and thus the magic as well. It is also worth noting that Red Talon has not been seen (aside from some imposters) since the cataclysm.
Many theories exist as to what caused the cataclysm, but there has been little proof for any of them. Because of the magical nature of the catastrophe, many believe that the Tyrian Empire was tampering with forces they didn't understand or couldn't control and destroyed themselves. Others firmly believe the gods had a hand in the event (either as punishment or as a warning). Some see it as the first element of Chaos gaining its firm foothold on the world.
Most current scholars agree that the Third Age of Cadash ended with this horrible event.

Historical Basis

Evidence of the Cataclysm can be found throughout the world of Cadash, but is most common in Reluria . The Rift is essentially a poisonous mass of ruins filled with wild magic and horrible monsters. But a traveler doesn't need to journey there to find evidence. Buried ruins from the massive Tyrian Empire can be found all over Reluria, often showing some kind of damage from the massive tremors or magical powers that erupted at the time.
Some scholars hope that treasure hunters in The Rift will find documentation or clues to the cause of the cataclysm. Unfortunately most adventures who attempt the delve either never return or only come back with material goods that shed little light on the issue.

Spread

The Cataclysm is well known all across Cadash. The impacts are still being felt and even young children know of the event.

Variations & Mutation

There are too many variants of the tale to cover here. Most revolve around why it occurred, but what exactly happened is also becoming more and more mythic.