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Around the year 429 BCE, the Gateway to the Lost City, which connected Atlantis to the surface world, was visited by the Spartan misthios Kassandra. There, she discovered her biological father, Pythagoras, along with the Staff of Hermes, which had kept him alive for a very long time. Together, they used the Atlantis artifacts to seal the entrance to the city.
Pythagoras compared Atlantis' function to that of a library, containing all of the knowledge of the Isu; including their physiology, scientific advancements, historical knowledge, culture, and beliefs.