The Cataclysm was the turning point of all history in this world, and marked the beginning of what is now known as the "Deep Sea Era."
According to what Nina had related, Duncan had finally begun to grasp the earth-shattering change that had once occurred in this world, and realized that this world had not always been as eerie and dangerous as it was now—
According to historical records, the world before the Cataclysm was once a prosperous and safe paradise.
Back then, the oceans were not the "Endless Sea"; the limited seawater did not cover over ninety-five percent of the world's surface as it does today; back then, humanity lived on vast and safe lands, and even the seas did not contain hazardous anomalies like the Spirit Realm, the Subspace, or similar dangerous phenomena.