The theory of phoenix nirvana comes from Mr. Guo Moruo's book of the same name, and the prototype comes from the poem Phoenix Stone written by Yang Weizhen, a scholar in Yuan Dynasty.
Guo Moruo said in The Nirvana of Phoenix: "Phoenix burns itself to ashes every 500 years, and then rises from the ashes, circulating endlessly and becoming eternal life."
Extended meaning: Phoenix is the messenger of world happiness. Every 500 years, it will bear all the unhappiness and hatred accumulated in the world, throw itself into flames, set itself on fire, and exchange the end and beauty of life for peace and happiness in the world. It is also after the body has experienced great pain and tempering that they can be reborn with a better body.