Black Ichor, a dark and tarry substance, sometimes bubbles up from beneath the ground without warning.

Black Ichor has many remarkable properties.

The chiefest and most wondrous of these is the way in which it mutates inorganic and organic substances it comes into contact with, transforming them into entirely different substances. Even a few drops of Ichor is enough to produce this effect.

In the hands of an amateur, the transformation is random, and it can only effect a small amount of the target substance.

The Imperial Commission, however, has learned how to direct this process and vastly increase its efficiency.

This guided transformation is known as ichorwerk.

Black Ichor has to be carried in specially prepared obsidian flasks. Even these decay and twist over time, rendering the Ichor inside worthless.

Commissioners - also known as Ichor Savants - study how to manipulate Ichor.

Commissioners can usually be identified by their numerous bodily mutations, earned through long and diligent hours studying Ichor on behalf of the City.

As a rule of thumb, the more mutations a Commissioner has, the more senior they are.

Mutations are therefore a source of great pride for Commissioners.

Within the Commission, an Ichor Savant is judged by the quality and quantity of substances that they can reliably transform. Any neophyte can turn rock into gold, but to turn gold into grain - edible, digestible grain? That takes a master.

To become a Commissioner, one must petition the Imperial Commission. If successful, applicants are required to pass an exam administered by the Commission. The contents of the examination are unknown.

The influence of Black Ichor accounts for some of the peculiarities of Rastaban.

For instance, its farming practices. Although there are farms outside the Embrace (and personal plots of land used for cultivation within the city), a significant proportion of Rastaban's food is produced by ichorwerk.

Furthermore, the efficiency with which an ichorwerker can produce precious minerals is one of the primary reasons that these are not more highly prized within the City.

By Imperial Decree all Black Ichor belongs to the Regent and owning any without permission is Treason.

The Imperial Commission and its members have permission to own and study Ichor by Imperial writ.

The Commission therefore have a monopoly in this area.