The watermelon cutting symbol relates to the moon, so Chen Qinghan suspects that this symbol belongs to a faction of the Celestial Maidens clan, a faction that has continued since ancient times.
Perhaps this faction was the builders of our ancient tomb, similar to tomb-building artisans, and that's why they possess the layout map of the tomb.
Chen Qinghan's speculation is reasonable, but I think it's not that simple.
Bi Shi is a criminal within the clan, and the watermelon cutting plan is to take her out of the 'cage', which certainly isn't a pure intention.
If the Heavenly Maiden Clan didn't have strange abilities, no matter what trouble they caused, they wouldn't be a threat. But people in the Heavenly Maiden Clan are somewhat different from ordinary people, so who knows what mess they might create.
