Murong Ziying is the only character in the main cast to achieve immortality, and he is also the one who issues the quests.
At the very end of the game, he shares his reflections accumulated over more than a century:
"It matters little whether things are good or bad. Human life is an empty dream; youth fades to white hair in the blink of an eye. Only the Heavenly Dao remains constant, cycling eternally without change."
Chapter 208