The exact moment the purification wall that they all had worked hard for disappeared, Wei Jiayi was ready to get them away from that place immediately. He almost acted irrationally because of his worries that might have gravely ruined their plan.
Regardless, at that moment, nothing was stopping the black smoke from spreading further as it moved to quickly follow it's master's orders as it could now freely enter their spiritual points if they were not strong enough to protect themselves from it.
He did not know that a wraith could produce black smoke of this large a scale. The enemy had set up a boundary spell and also controlled an army of YinYings.
'He is really strong.' Wei Jiayi already knew that. He was just reminding himself of how dangerous his enemy was.