"Plague Book"—a special book associated with the origin of disease and unique to the Source Plague Zone—even when officially bestowed upon an individual, still imposed certain restrictions on reading.
These restrictions were directly related to the purity of the individual's disease.
Those who first obtained the Plague Book could usually read only the prologue. To enter the official chapters, they needed to raise their purity in matters related to plague*.
*Purity referred to the concentration of the disease associated with an individual and the Source Plague Zone.
For example, for cancer patients, it included the total number of tumors and the purity of their pus.
For the True Dead, it included the concentration of death plague and the complexity of their fungal bodies.
For monks, it included the number and hardness of their iron chains, as well as the depth of their pain.
Purity could be raised through exploration, study, and cultivation along one's path of disease, gradually unlocking the Plague Book's later contents without skipping ahead and risking premature contact with material that the individual could not yet withstand.
However,
among all the Source Plague Zones, the Abyssal Skin Factory was an exception.
Because of its distinctive Old World industrial style, the factory imposed relatively strict purity controls on the skin slaves under its command.
For an individual to raise their purity, self-study and cultivation of disease were not enough. They also needed to rely on the advanced skins granted by the factory to achieve a true increase in purity.
Therefore,
a skin slave had to display their own potential, express absolute loyalty to the factory, and make concrete contributions before they could be gifted an advanced skin—and only then could they read the entire contents of the Skin Bible.
The factory's actions undoubtedly strengthened its control over the