C3741 Quietus Lord.

"Since this man has obtained the Vast Nether Magic Cube I left behind, he must have seen the No-heaven Book as well. To be able to see the No-heaven Book alive, it seems like he isn't a simple man."

Because what was left behind was only a wisp of remnant will within the seal.

Therefore, Vast Nether God didn't know what method Luo Xiu used to break the seal