Duan Ling Tian decided to act after five days had passed because he estimated that the Verdant Prairie Celestial Emperor and the Howling Heaven Celestial Emperor would arrive at the location he lured them to at that time. Once they arrived at the place he designated, it would take them at least five or six days to rush back to the Heavenly Pool Palace.
"Alright, I'll convey your message to them and speak to them. They'll definitely cooperate since this is a golden opportunity for all of us," the old woman replied as her eyes flashed near the end of her words. This was the best chance for them to regain their freedom. After all, even if they failed, they would only be thrown back into prison.