Even the Mirror Demon King couldn't detect their presence, of course, as soon as they left the lake bed and reveal their figures, the Mirror Demon King would immediately discover them.
As for the wind bird of the Dragon Temple, it was impossible for them to enter Flame Demon City. Once they entered the Mirror Demon King's spiritual radar range, any wind bird would be easily annihilated.
...
Thus, the three Hell Knights hid inside Flame Demon City, and no one knew it, as they quietly waited for the final battle to occur.
The contest for being the strongest human, between White Wolf and Jiang Shang, took place as they sat quietly four hundred miles north of Flame Demon City atop a mountain peak, waiting for the final battle to occur.
