One could tell that the strength of that immortal was not to be underestimated.
Old Man Yang continued, "However, based on my observation and analysis, that immortal seems to still be cultivating some kind of special formation. Because every once in a while, powerful energy fluctuations erupt from here—extremely powerful ones, strong enough to make the entire prison shake.
"Judging by those energy fluctuations, these are not natural occurrences, otherwise they wouldn't be so regular. But I don't know what specific formation it is yet."
Chapter 1028