Back when the competition had just started, the twins asked Sister Orb to start taking control over the Cultivation Suppression Formation. One must not forget that Sister Orb always had this ability, but the time needed to take control over it depended on the scale of the formation. Then again, the twins knew they would spend many years there, so Sister Orb might as well get started.
In the end, Sister Orb eventually succeeded in her task. The only problem was that she couldn't use it yet. After all, no one had been to the central region before. It would be incredibly unbelievable if the twins' region took control over it. However, the attack on the central region was just the perfect opportunity! No monitoring while they had another job to do. Rean and Roan could simply pretend that they had followed some hidden path and took the formation without anyone noticing.
