Actaea

Yes, and the ships sail south into a black hole, where goods are taken away and others are brought in, airplanes transport people through the same black hole, and the Arcondians themselves came from a parallel world, just like the emperor who didn't exist, but his son appeared from somewhere.

It's actually quite simple. On the ships, they transport all sorts of troublemakers and other citizens who undermine STABILITY. Where did they disappear to? They simply returned to their historical homeland! The Arcondians themselves are local residents; the history textbooks were fabricated by the government, and fortunately, they tell about events from a century ago. As for goods and money, it's even simpler – they are stolen by officials, and the level of corruption is one of the highest in the region, while the common people are fed fairy tales about the mainland.