Meng Po is the goddess of forgetfulness in Chinese mythology, who serves Meng Po soup on the Bridge of Forgetfulness or Nahe Bridge. This soup removes a person's memory so that they can be reincarnated without the burden of their past lives.
There are several realms under the earth. Meng-na serves in the Earthly Realm, the Chinese realm of the dead, in the Tenth Palace. Her task is to ensure that souls preparing for reincarnation do not remember their past lives or their time in hell.
To do this, she collects herbs from the various ponds and streams on Earth to make her five-flavoured tea of forgetfulness ('water of forgetfulness'). This is given to each soul to drink before leaving Diu. This drink induces instant and permanent amnesia, and all memories of other beings are lost.