Destruction of Terra
Destruction of Terra: The mistaken belief held by the population of the Distant Fringe that the implacable, all-powerful other-human Vilani Imperium crushed the nascent Terran Confederation during the conflict that they call the Final Interstellar War.
The humans of the Distant Fringe believe that in 2147AD the Vilani reduced Terra to a radioactive wasteland and absorbed the shattered remnants of the Terran Confederation into the ancient Vilani Imperium. They truly fear that the Vilani will eventually track them down and attempt to absorb or destroy them. They have no idea that the Terrans eventually conquered the Vilani, or of any of the subsequent history of Charted Space.
Many of the pocket empires in Holowon Sector and Amderstun Sector descend from emigration efforts around this same time that held this same belief at first. News of Terra's survival eventually reached these colonies over the course of the Second Imperium.
The Final Interstellar War saw a Vilani fleet occupy much of the Sol system in late 2147AD, and launch an orbital nuclear bombardment of Terra itself: it was during this bombardment that couriers were dispatched with orders to set the Last Armada under way. The Armada, assembled under the aegis of the Expedition, fled to rimward in utter secrecy following routes pioneered by the Five Year Missions, carrying with it what it believed to be the last remnants of Terran culture and society. After an epic journey lasting for more than a century, and at the very limit of their endurance, the Last Armada found and settled the Demon Cluster, naming it the Distant Fringe.