Return to Atlantis Once More

Earth was part of a universe-wide collection of races, known as the Imperium of Sovereign Races Fleet (ISR). Worlds capable of sustaining the various life forms of the ISR were few, and the races who needed more space to live were many. So, the most important rule for all ISR worlds was to wait for a planet to be terraformed for your particular race's needs and then colonize it. But humans, unlike all the other ISR races, were a short-lived race, barely living to a thousand, when all the other races easily lived beyond two. Humans made up for their short lifespan by being fast breeders. Where other races took a millennium to reproduce thousands, humans could reproduce billions. Because of these traits, humans needed more and more colonies to accommodate their growing populations. So, any world terraformed to standards in which human life could thrive, Earth would quickly claim and send in colony ships. When the ISR had enough of Earth's violations of colony rights, war on Earth was declared. Earth, however, had been planning for such an event and was preparing for the war, which they knew would eventually come. To this end, there was Atlantis. Atlantis was Earth's most advanced research and development facility, located on an island in the middle of an ocean. And deep within this facility was the largest, most sophisticated Super Dreadnaught ever conceived. It was bigger, stronger, and faster than any ship the ISR possessed. But it was years away from being completed when the ISR demanded surrender or death. Earth chose to fight and sped up production. But, the ISR eventually beat back all of Earth's forces and eliminated all but one Earth colony, Eden, which had broken away from Earth's control, long before the war was declared. The ISR could not break through Earth's defensive shield, so they did the next best thing: they melted the polar ice caps and drowned humanity and sent Earth back to the Stone Age before they could complete and launch the Atlantis. Tens of thousands of years later, the ISR has returned and is threatening to cause another extinction-level event unless Earth surrenders and abandons its colonies in the SOL solar system. However, this time, the ISR has received assistance. The Earthling Preservation Society had infiltrated the ISR and was willing to not only help Earth with valuable information but also find the super dreadnaught, which they hoped was still buried deep inside Atlantis. But first, they had to find the island, Atlantis. They needed to hope that the ship was finished, that they could get it into orbit around the Earth, and that it would be strong enough to force the ISR back to the negotiation table. That was a loss of hope, with little to no backup plan. But any hope was better than a third human extinction event.