What's the difference between cow's head and horse's face and black and white impermanence?

Although tauren and black and white impermanence are both messengers of hell, they manage different things. Black-and-white impermanence is the ghost that leads ghosts into hell, and the cow's head and horse's face are the ghost that guards the gates of hell. Nowadays, there are black and white impermanence in many film and television dramas. When someone dies, black and white are impermanent and come back to collect ghosts. When you go back, you can see the cow's head and horse's face at the entrance of the underground palace.

The main duty of black and white impermanence is to catch ghosts. Ghosts only exist when people are dead, and it is black and white to catch ghosts in hell. Black and white are impermanent. One is dressed in black, one in white, one in black and one in white. Very easy to identify, and they all appear at the same time, and they hardly act alone. Black and white are impermanent, because there is no emotion, and they are the two most serious ghosts. They will not be moved by human crying. They only have responsibilities in their hearts, because they have no sympathy and empathy.

Cow's head and horse's face were originally two ghosts in charge of ghosts in the underworld, and they were also Yan's right-hand man. At first, there was no horse face, only a cow head. When the tauren was human, he became the ghost of the tauren after his death because he was not filial to his parents. The implication is that he became a cow to repay his parents, and later he had a horse face for symmetry.

Later, Niu Mamian was demoted as a gatekeeper because of his mistakes. At that time, Niu Mamian often played chess in a ruined temple. Then, in order to intercede for them, a member of the horse called a fortune teller and invited them to eat and drink. After dinner, Niu Mamian did something against the rules behind Yan's back, and Yan found out. In order to punish them, Yan let them stay at the entrance of hell forever, on the one hand, to prevent ghosts from escaping, on the other hand, to make up for their mistakes.