The world has mysteries that we can never explain. Cities that no one built, languages that no one can read or speak, technologies no one can understand in the slightest. All we know is that they have always been there, and that if we want to know what happened to them, we have a long ways to go Unknown to most of the world's inhabitants, the world resets every thousand years or so. No one dies; everyone's memory is wiped from that point, and we all start at square one, with basic knowledge we barely understand, surrounded by things we don't understand, and eager to learn more.