The Ending Winter

Brother,
Look, I know you, so I know that when you question the boss, you're coming from a good place, but he and the rest of the crew aren't going to see it that way. Objecting to an expedition to a previously undiscovered ruin is a really fast way to lose us a profession, even if there are rumors of monsters in the area.
Do you remember Nan, back in the old village? You were pretty young, so I wouldn't be too surprised if you don't. She would always take care of us when Da and Mum would leave to sell their wares in the city. At night, when you couldn't sleep, she could just stroke your forehead and hum a lullaby, and you'd be down for the night. She couldn't get that to work for me, though. Instead, she would tell me stories she heard as a child. Heroes, monsters, kings and old magics the scholars I've met scoff at and dismiss as superstition, but the ones that stuck with me the most told of the Winter, the end of the Ancient Age.
Nan told me that before the world we know came to be, Themere was a paradise blooming with magic beyond the wildest dreams. When the God of Betrayal tempted humanity to rebel against the heavens, the forbidden power he used could only be matched by the divine weapons wielded by the Gods. When these forces met in battle, however, the sheer magical power present among them could not be contained, and Themere itself intervened with the Ending Winter, a magical void so vast it drained nearly all of the magic in the world. Since then, even the greatest magical feats known to all mankind are child's play compared to the ancient powers. Only relics like the weapons of the Old Lords hold power even approaching the Ancients, and the scholars are willing to pay fortunes to study them.
That means we make a fortune if we manage to find something of the Ancient world. The boss has a solid lead on ruins that may be untouched for thousands of years. Even if there's monsters about, whatever we find, it's worth the risk.
You don't even need to be so worried in the first place. The boss convinced one of the mage scholars from the academy to tag along, and even paid a handful of the Steelborne to join for extra insurance. Between all of them, there's nothing that can stand in our way.
Keep this on you as a reminder not to say anything dumb again before we get rich.

From the one that got our parents' smarts,

Orsin

Summary

An apocalyptic event that marked the end of the Age of the Ancients, the Ending Winter is the name referring to the most powerful instance of the negation of magic in all of history, resulting in the loss of nearly all magic in the world, for which the Age of Ancients was known. While each culture has its own myths on the Winter and what led to it, the true cause is a matter of much speculation and debate, and given the fragmented nature of records of the time, may never be discovered. Without knowing the true cause of the Ending Winter, a means of predicting or preventing another event like it cannot be developed.

Date of First Recording

4000 years ago, a codex was made piecing the event together from references to it in other recorded myths.

Date of Setting

End of the Age of Ancients