Since Pangu opened the sky, the chaotic heaven and earth were separated, and the world was instantly divided into heaven and underworld. Later, when Nuwa created humans, the human world appeared in the world. Among the three realms, only the heaven is the most holy, and the underworld is the most mysterious. However, mediocre humans are jealous of the heaven and the underworld, and if they want to live in the heaven or the underworld, they start to practice. People with high qualifications, after a lifetime of dedicated practice, become either immortals or monsters, but they can never reach the heaven or the underworld, and suffer from the inability to return to the human world, so they linger on the edge of the two worlds for a long time. After hundreds of thousands of years, the number of people in this group creates the fairy world and the devil world. At that time, due to the prevalence of the practice of cultivation, many flowers, plants, trees, birds and animals, etc., Became popular and gained cultivation. And because he has grown up in nature for a long time, he is simple and ignorant by nature, absorbs the essence of heaven and earth, and succeeds in practice earlier. In order to maintain the balance of the five realms, the Emperor of Heaven specially established the spiritual realm for him. To demons, they are children of spirits and demons. After that, there were more and more fairies, and the demon world was naturally formed. Since then, the seven realms have been formed and the world has been balanced.