Judges are the messengers of the Central Government, sent out to punish delinquent cities. They have the ability to control programmed "seeds," causing explosive growth. After a disease breaks out among the "Children of Babel," those Judges who're given power through Central's research, Central requires the data of a natural Judge like Sion. However, Central is also interested in the legend of the "Heavenly City," which Sion is named after; what could their true purpose be?

(Source: Storm in Heaven)