Unlike the omens that precede the Three Disasters, the Nine Tribulations often appear silently and imperceptibly. Tribulation seekers are usually unaware of its approach, which arrives quietly, as was the case with Sun Wukong just now, who fell silently into the thrall of a heart devil, almost leading to demonic possession and irrevocable doom. Fortunately, Zi Lan Fairy appeared in time, or the consequences would have been unthinkable!
During the Three Disasters and Nine Tribulations, it is forbidden for outsiders to disturb the one undergoing the tribulations; otherwise, they would be seen as challenging the Heavenly Dao, and the intruder would also fall into disaster. It can be said that it was fortunate that Jiao Demon King had earlier persuaded Macaque King and the others to refrain, or they might have also triggered the heart devil, which would have complicated matters significantly!