Why is it that in every manhua that I read where there's a Tang clan they're always associated with poisons
BASTA PINOY AKO YAWA KAYONG LAHAT!!!
Because they a old book, i think it was called "Collected Schools of Martial Arts' by Wan Laisheng.
Basically a compiled book of observation. From what i remember it was based on Elder Sister Tang and her usage of Five Posion Sands. Thats the extent of that rabbit hole i remember.