Strongest Cultivator

*He had a disease, a disease of eternal youth, immortality!
He had seen Pangu open the sky before, and he had seen Da Xi who had been bewitched by the heavens!
He was once the teacher of the Emperor. He taught the Qin Emperor how to destroy the six empires. He also traveled 10,000 kilometers to find scriptures with Tang Xian!
He had seen the blue sea turn into mulberry fields, and he had also seen the alpine plains!
A long dream for thousands of years, and I will live forever in this world!
What is his story ？When you have infinite time what are you going to do ？