In a grand era, there are countless smaller eras.
Under the suppression of an emperor, the path of cultivation for all beings becomes increasingly difficult, until... that emperor reaches the twilight of his years.
During the years when an emperor transitions from prosperity to decline, there are periods of decay, of the end of the Dharma, and of resurgence... In these countless smaller eras, there are countless invincible beings. Some choose to break their shackles and live without regret, while others, seeing no hope ahead, choose to seal themselves away, waiting for the path of the emperor to reopen.
Among the invincible, there are both the strong and the weak.