Qin Kexin

In the Supreme Ancient Immortal Realms, there were some secret forbidden grounds that only a rare few had the qualifications to enter. And after they entered, it was very difficult for them to leave alive.

Many of such forbidden grounds were not known to many people because it was extremely rare for people being able to succeed in leaving them alive, hence, this led to only very few people knowing about them.

For example the Heaven Vault. The Heaven Vault was once something extremely few people knew about. Only after the secret of the Heaven Vault was revealed did people of the world learn about it.

There were still some mysterious grounds where the secrets within them weren't resolved yet.