Preservators and their related facilities are one of the means used by human beings to evade observers and preserve human blood. Through this large-scale freezer management facility, a large number of people have entered a dormant state, avoiding observation by observer, and waiting for the day when human civilization will be reborn. Before that, the entire facility was managed by the preserver - a semi-mechanical and semi-human consciousness (due to the fear that the purely mechanical AI would be hijacked by observers, the preserver is not an artificial intelligence in ordinary sense).