It is said that there was once a woman on earth who had a stone for a heart. Even when she became a mother and gave birth to two beautiful twins, they did not arouse any maternal feelings in her. As the crying of her children seemed unbearable to her, she left her sons without a word and abandoned them to their fate. This is the legend of the Emperor of Heaven and his assistants.
A couple of brave people took in the children and raised them. The two brothers gave much joy to their adoptive parents. The only reproach that could have been made to them, perhaps, was that they were very reserved and rarely expressed feelings. But they possessed, on the other hand, a prodigious memory without the slightest effort, they were able to tell everything they had seen, read or heard since birth. The Jade Emperor was aware of this extraordinary faculty and summoned them close to him. He appointed them first advisers and assistants. He entrusted to them the fate of men and their souls.
Since then, Nam Tao, sitting on the left of the Jade Emperor, has kept the register of all the men who live on earth. In his book of Destiny, all human existences, from birth to death, are recorded. But Nam Tao has no need for this book because he has an extraordinary memory.
The other brother, Bac Dau, sits to the right of the Heavenly Emperor and keeps the register of the dead. He also does it without the list.
These two ministers can be seen in the Night Sky: Nam Tao sparkles in the form of the Southern Cross. While Bac Dau takes on the features of Big Dipper.