From the Game's Introduction:
Shining Atlantis, jewel of the Mediterranean. A glorious city, founded on the tripartite pillars of sorcery, science, and philosophical enlightenment. Unmatched in power, unrivaled in beauty, and unsurpassed in knowledge, it is the center of the ancient world's culture and politics, and it's dying. Within six months, a magical conflagration of unknown origin will consume the city, sinking the very earth on which it rests into the sea.
No external enemy could accomplish this atrocity, though there are many with the motive to try. No random natural disaster could sink the island nation, its sorcerous protections are too complete. Atlantis's doom came from within. It could have been an accident, a malfunction in the city's life support spells, or a sorcerer's duel that grew out of control. It could have been an act of malice, the handiwork of a psychopathic enchanter. It could have been civil war, the natural consequence of open conflict between thousands of magically active individuals. It's impossible to say. No records remain, and the disaster left no survivors. Only one thing is certain. The end was inevitable.
For all its knowledge and power, Atlantis carried the seeds of its own destruction. Native Atlanteans focused on scholarship and magical power, disdaining the simple physical labor necessary to sustain even the most wondrous civilization. To fill the need, Atlantis resorted to slavery, using their powerful weapons to intimidate their neighbors into paying human tribute.
Its once-proud government, the Council of Atlantis, has degenerated from a model democracy into a group of petty, squabbling oligarches, concerned only with their own power and privileges. In the city's final months, council sessions are dominated by personal vendettas, its members using the law as a weapon in their own petty feuds, rather than as a tool to improve the lives of Atlantis's citizens.
The city's scientific and magical research, once tempered with wisdom and kindness, loses all perspective and restraint. Scientists create new and destructive technologies with no regard for how they'll be used. Sorcerers conduct foul experiments on unwilling people, justifying their excesses in the name of knowledge. The explosion that destroyed the city was nothing. In the final months, weapons are created that can shatter continents and boil oceans.
All these problems and more are what doomed Atlantis. The actual disaster was one of a thousand possible mishaps that could have destroyed the city. Even if it could have been prevented, something else would have eventually come along.
The Last Days of Atlantis chronicles these dark times, taking characters through the events leading up to the end. Players take on the role of one of the city's inhabitants, experiencing their lives in the weeks and months leading up to their untimely deaths. Perhaps they are the arrogant sorcerers who ultimately destroy Atlantis. Perhaps they are some of the few remaining uncorrupted civil servants, struggling valiantly to prevent the imminent disaster. Perhaps they're slaves, wanting nothing more than to escape the wretched place before it slides into the sea. Decadent and magical, Atlantis inspires as many stories in death as it did in life.