Ling Tian and his allies were far more capable of taking cities and seizing territory than Chi Xue and his people. Even without counting hidden powerhouses like Feng Lingzi, if Ling Tian's side could stall until the runic array set up by the Rune Cultivators became strong enough that Chi Xue's side couldn't break through, then they would no longer need to worry about Chi Xue capturing the Rune Cultivators and learning how to use runes.
If Chi Xue's side couldn't overcome the runic array, there would be no point in remaining in the western region of the God Realm. Ling Tian's side could simply wait until Chi Xue and the cultivators from the other major factions left, then move against the Rune Cultivators themselves. That way, they could claim the art of rune application all for themselves.
After realizing that Feng Lingzi and the others had been hiding their strength, Chi Xue and his people knew that Ling Tian's side was powerful enough to break through the Rune Cultivators' array, even though none of the other major factions could.
But then Fei Ling raised a question: since Feng Lingzi and the others had hidden their strength before, surely they would still have reason to keep their true power concealed now.
Ling Tian and his companions had faced several perilous situations in the Beast Soul Realm. For instance, if the Technology Cultivators had led an attack into the You Hun Realm while Feng Lingzi and the others still hadn't revealed their true strength, they must have been holding back out of caution. Otherwise, with their power, they could have destroyed the Technology Cultivators' base in the eastern region of the God Realm long ago, and no longer needed to fear them.
"Perhaps Feng Lingzi and the others had their reasons