The Great Falling
The Great Falling was a catastrophic biological natural disaster, in the form of an unstoppable plague, that killed men, animals, biomechanoids, and many other living creatures, that first appeared on the The Syndicate world of Ember about 700 years ago, and which swept the planet, killing billions in its wake. Despite the best efforts of the Syndicate, the plague eventually forced them to abandon Ember, and flee to their other worlds where they continued their vast and unchecked scientific research, genetic experimentation, and more. The Great Falling eventually ran its course, after wiping out over seventy percent of the planet's population, but not until long after the Syndicate had both fled, and left behind the planet, never again to return.
The Great Falling is a mega pandemic of Extinction Level Event classification that was, and still is, is also known to the surviving local people as "The Great Cleansing", "The Purging", and many other names, due to its extensive and catastrophic nature. However, it was later revealed that this great plague was not actually real. While many people died, it was part of an elaborate ruse by the Chief Director at the time to convince the Syndicate, primarily the Alien Brotherhood to abandon the planet. The plan was, drive them off of Ember, and make them flee to Offworld for a time, while preserving the planet in the meantime, and then return at a later date and reclaim it again, but without the Brotherhood. However, those plans fell through and the planet then remained abandoned well past the time of Journey's End.