The beginning of the third volume of the Three Bodies did not talk about the female demon in Constantinople but directly revealed the crisis facing human civilization. Under the invasion of the Three-Body People, Earth's civilization suffered an unprecedented blow, and mankind was facing a crisis of survival. In order to let readers better understand this background, the Trisoloid used the " Dark Forest Law " to explain the competition and conflict of civilizations in the universe. This law believed that civilizations in the universe were like creatures in the forest, suspicious of each other, guarded against each other, and attacked each other. Because they could not know the intentions of other civilizations, each civilization would do their best to protect themselves from being discovered and attacked by other civilizations. In this context, a certain female demon in the Dark Forest became a metaphor that symbolized the threats and challenges facing human civilization. This female demon was not a real person, but a symbol that represented the difficulties and dangers faced by human civilization. At the same time, it also hinted at the reason and purpose of the Three-Body People invading human civilization.