Ace's smiling face suddenly turned serious when his soul sense finally calmed down, but he knew something must've big happened outside since it lasted for whole five minutes.
Noa also noticed the change in Ace's expression and couldn't help but asked with uncertainty, "Leader, is there something wrong?"
Ace knew Noa can't sense what just happened outside, so he told her how he felt that mysterious undulation for a whole five minutes, and then it suddenly vanished.
"It might be a powerful surveillance formation that can also lock cultivators with a specific realm and, by how powerful that undulation was, it seemed, even a Soul Realm Expert will find it difficult to escape this formation suppression. We're lucky this room can evade that formation, or we might've encountered some terrible luck." Ace's voice was grave in the end.