There is a novel I read, ages ago. It is a Cultivation novel in which the shou turns into I think some kind of beast snake, and ends up being regarded as a pet for the gong. He later becomes that gongs own discple when he joined the sect. But I for the life of me can't seem to remember the title name of it!
https://www.novelupdates.com/series/rebirth-of-a-useless-waste-number-one-evil-immortal/ I remember he became a green snake
@Rilise It was this one! Ty!!! @Juju48 thank you for helping me as well. I saved that one for further date so I can read it as well~