Atlantis itself had been a small above ground continent with many human settlements, when an event 10,000 years ago called the "Great Cataclysm" caused it to be submerged into the sea. 2,000 years later, a group of "Homo mermanus" made the ruins of the human settlements in Atlantis their home and went on to develop a society there using as much of the material as they could scavenge from the wreckage. Many of the warring tribes united under a single emperor (although by the 20th century there were still some barbarian tribes).