An ancient tradition claims that in the beginning, there was a peach tree that grew on Mount Tu Shuo in the Eastern Sea that was so enormous that its branches spread out across a territory that was several thousand square li in size. The gap created by the lowest branches, which angled toward the northeast, became known as the “Door of the Devils” (kuei) and was used by millions of demons to enter and exit the world. This tunnel was to be guarded by two ghosts known as Shên Shu (or Shu Yü) and Yü Lü. They were given the assignment. Those who had caused harm to humans were promptly chained by the survivors and thrown to the tigers to be eaten. After hearing this, Huang Ti had pictures of the two spirits made on peach-wood tablets and placed them over the doors in order to ward off malevolent spirits. This ultimately resulted in the attachment of the miniature figurines or plaques to the front doors of the general populace. They were gradually replaced with paintings on paper that were glued onto the doors. These paintings depicted the two spirits equipped with various weapons, such as bows, arrows, spears, and so on, with Shên Shu on the left and Yü Lü on the right.
However, in later ages, two ministers of the Emperor T’ai Tsung of the T’ang dynasty named Ch’in Shu-pao and Hu Ching-tê managed to displace these Door-gods as the most popular deities among the general populace. T’ai Tsung had become ill, and his imagination led him to believe that he could hear demons wreaking havoc in his bedroom. After questions about the nature of the illness, the ministers of state were told by the physician that His Majesty’s pulse was hot, that he seemed agitated and had visions, and that his life was in danger.
There was significant apprehension among the ministers. After the sick Emperor had informed the other physicians that, although everything was quiet during the day, he was sure he saw and heard demons during the night, the Empress summoned other physicians to a consultation. Ch’in Shu-pao and Hu Ching-tê stated that they would sit up all night and watch outside his door. The sick Emperor informed the other physicians that, although everything was quiet during the day, he was sure he saw and heard demons during the night.
As a result, they stationed themselves outside the palace gate throughout the night, fully armed, and the Emperor was able to sleep undisturbed. The next day, the Emperor expressed his gratitude to them in a heartfelt manner, and from that point on, his illness began to improve. The two ministers, on the other hand, kept their vigils until the Emperor told them that he would no longer impose upon their willingness to sacrifice themselves and that he would no longer need it of them. He gave the order for them to paint pictures of themselves in full battle gear and then stick those paintings on the doors of the palace to see if it would not have the same effect. There was silence for a few nights, but eventually, the same ruckus could be heard coming from the direction of the palace’s rear gates. Minister Wei Chêng made an offer to undertake the same job that his colleagues had done at the front gates, but this time they would do it at the rear gates. As a direct consequence of this, the Emperor’s health was completely revived in a matter of days.
As a result of this, Wei Chêng is often connected with the other two Door-gods, sometimes appearing alongside them and other times taking their place. Nearly every door in China has an intricately colored picture of a mên shên, which is replaced at the beginning of each year in celebration of the New Year.