Zhu Zemin's weakness

Walking briskly towards the corridor inside which he stored the vault, Zhu Zemin kept on looking all around to make sure no one was following him. 

The vault possessed something which Zhu Zemin valued more than his own life. 

Originally when his father had shown him the vault, changed the handprint which needed to unlock the vault into Zhu Zemin's, and revealed the details of the treasure inside it. 

Zhu Zemin scoffed and wrote it off as the stupidity of all the previous generations to store a treasure which they didn't know what it did so safely. And even go as far as wasting so much money to do so. 

However, when someone from the Yin Plundering Sect came to visit him and asked him about something which matched the very treasure his family had kept a secret for generations, Zhu Zemin started believing all the stories his father told him about it.