Based on the story of the previous "swdol" console game version, the Dream of Mirror Online is a world that features sacred artifacts. The sacred artifact Kunlun Mirror that created the world, like some other artifacts in swdol I online familiar to hard-core players such as the swdol and monster buster pot, was a sacred artifact from mythical ancient China. Those sacred artifacts all have the powers to create and destroy the world.
Among those sacred artifacts, the swdol represents the power of culture; and the monster buster pot symbolizes the creation of the world. The Kunlun Mirror was originally created to record everything. In the world created by the Kunlun Mirror, there is another world in the mirror that reflects the real world; it saves a copy of everything in the real world in the Kunlun Mirror world. Time does not exist in the Kunlun Mirror world but only in memories. The managers of the Kunlun Mirror world, twelve Mirror Kings, are responsible for the operation of the Kunlun Mirror world.
We don't know when it happened, but the Kunlun Mirror world has lost most functions and is not able to precisely reflect reality. Many mirror kings have disappeared as well. The reason behind those problems is because of the "delusion" created by human beings in the real world. When those "delusions" were reflected in the Kunlun Mirror, they were turned into various odd life forms and interfered with the normal operation of the Kunlun Mirror.
To solve the Kunlun Mirror crisis, the mirror kings started to call the real world human beings entering the Kunlun Mirror to assist the kings to deal with problems created by the delusions in the human mind. That's why the players exist in the Mirror world. Since those "delusions" will turn into various dangerous monsters and ghosts in the Kunlun Mirror world, in order to let the helping visitors feel safe, the mirror kings guarantee that they will not really die in the Mirror world.