C1600 Can You Give Me the Letter
In the letter, Chang Xu explained some things that he could not say to Mo Nan in person. He also told Mo Nan his hard work.
The Divine Meaning Heaven Equal Spell was obtained by him in a desperate situation in the Upper Realm. That place seemed to have something to do with a big secret. He did not specify what kind of secret it was.
Perhaps it was Chang Xu himself who did not know.
In short