The ISAAC was a colossal sized type of ship that was used in the Before Land era, when most of humanity lived as sea nomads. They held a population of hundreds to thousands of crew-mates who would have spend their entire lives on board. Most historians believe that for some reason, the land was simply too dangerous to live on for thousands of years, but in the end the tides turned, and the land became more inviting while the sea grew dangerous. Thus became, the new era, After Land. ISAACs may provide context and details to The Great Mystery, which is the question of what life was life before the humanity fled to ISAAC ships.
Lost TechnologyIt is unknown why humanity has lost the knowledge on how to construct ISAAC ships, maintain them, and how to build and maintain the equipment that was on board the ships. Some modern technology on Gaia are reinventions of technology though to exist on board the ISAAC, such as the Artificial Womb, which allowed parents to have children without the burden of pregnancy. ISAAC ruins are highly valuable places for resources and for research. One of the most well preserved ISAAC ships lay by the The Mid-Summer Sea on the island Suwa-Isuaihovwenaparvu - Isle of Love, Hope and New Beginnings. The islanders carefully guard the ship, and are weary of people who seek to steal some of the sources on board. Alternative places for research would be Sanguin, but it is a hostile land to explore.
The technology for ISAAC deteriorated while humanity still lived on board the ships. It is intriguing for scientists to consider how several unrelated ships, who often competed for territories by calmer seas, lost their technology almost simultaneously. Such an event is part of The Great Mystery, a topic under constant debate and evolving theories.