It was common knowledge that Formations set up in open spaces would gradually weaken with time. After all, they relied on the Celestial Origin Energy of the person who had set up the Formations. Being in an open space and with the passage of time, there would inevitably be humans or beasts that accidentally triggered the Formations. Each time the Formations were triggered, it would exhaust a little of their powers. This was also the same for Formations that drew their powers from Celestial Crystals.
It was for this reason that the group of Celestial Kings were shocked when they discovered the Formation shrouding the peak of the mountain that took their collective strength to destroy was set up by Jiang Lan more than 100 years ago in his past life. How terrifying was the Formation to still be so strong after so much time had passed?