On the fifth day of summer, 235 SE, the Oncillan trading ship S.S.S. Raincloud lived up to its inauspicious name by disappearing without a trace in the vicinity of Barachiel's Horn. The Oversight Committee, breaking with its traditionally reactive role, immediately dispatched a delegation to investigate. The Port Authority of Gravitopolis disclaimed all knowledge of the Raincloud or its disappearance, and suggested that the Thin Ether phenomenon, by now quite severe, might be to blame. Certainly, this would not be the first ship to have been destroyed attempting to navigate an unstable region, although always, in the past, wreckage had been found. In any event, the Overseers departed without incident.

The leader of the delegation was the Committee's newest member, Josephine Tredimus, who despite her youth already was rising in the ranks as an Overseer as quickly as she had among the Aetherists. Always an outspoken opponent of the Hidden City in economic matters, in her speeches Tredimus now began to charge that Gravitopolis had developed a new weapon with which they had captured the Raincloud, and availed upon House Oncilla to demand either its return or monetary reparations. The Septarch complied, and issued his demands. The Gravitopolitans argued quite persuasively that they could not return what they had not stolen. Despite fierce division within the House, Tredimus ultimately convinced a majority that the Gravitopolitans were lying, and on the first day of the Septarchal year 236, House Oncilla declared war on the Hidden City.

Thus began the five-year conflict known in our history as the Gravitopolis War. The major fighting can be broken into two phases. In the first, lasting until the autumn of 238, the Septarchal forces repeatedly bested the hastily-assembled fleet of Gravitopolitan smokeships and in a series of raids was able to disable most of the Low Gates, all but destroying three of them. But the Ebon Legion, to widespread astonishment, declared its alliance with Gravitopolis, although their outdated ships were of little tactical value.

Toward the end of 238, two strange things happened. The Ebon Legion abruptly shifted allegiance, declaring its loyalty to the Septarchal lands and urging an immediate strike on the High Gate. Almost simultaneously, the Gravitopolitan Navy abandoned its purely defensive strategy and began a series of daring assaults on Oncillan ports.¹ Within months it became clear that the new Gravitopolitan smokeships were superior to those of the Flight Core (and of course, the new alliance with the Ebon Legion made very little difference). The Septarchal forces held their own through the winter and spring, but a steadily increasing number of Oncillan statesmen came to realize they were in serious risk of losing their autonomy over a matter of principal which had always been questionable. Finally, in the summer of 240, House Oncilla offered peace.

—Iohannes Edgardus Quobertius