This is a border town formation, with no one monitoring it.
So chances are that it identifies by attaching a tracking curse to any person with higher than expected spiritual energy.
All Jiushu had to do is use an inanimate object which has more spiritual energy than threshold.
Each curse takes away some spiritual energy from formation, no matter how minute.
She retrieved the rice paper from the space.
They made a hundred kites in two hours.
She made each kite with a small pocket where she can throw beans in. she filled the pocket with the beans steeped in the spiritual water. She had them prepared when MoQiu was searching for MoGan.
They are getting used now.
"ShenXin! Can you monitor whether the formation is active?" Jiushu asked.
Yes.