Zarvora becomes so powerful that she rivals the "mayors" who are officially the rulers. The librarians serving below her, whose hold ranks like "Dragon White" and "Dragon Red" are the only ones who really know about her machine, the Calculor, and what it can do.

One of the primary characters, Lemorel, is a lower ranking librarian who wants to escape her reputation as an infamous duelist who killed many people in her home town. After applying to work for Zarvora, she finds herself quickly promoted because of her expertise in mathematics:

Other librarians who meet her refer to Lemorel's mathematical research into "the Call". Another great (female) mathematician is also mentioned. However, she is already dead by the time we hear about her and so she does not appear as a character, merely as a motivating memory for her (male) lover who is also a mathematician but not nearly as talented as she was.

Zarvora is ruthless in her goal of building and utilizing the Calculor. Prisoners who show any mathematical skill are assigned the title of "ADDER", "MULTIPLIER", or "FUNCTION", and spend all of their waking hours participating in calculations whose purpose they do not understand. Furthermore, to maintain the secrecy of the project, they will never be released. But, as the Calculor grew, it also became more difficult to maintain this secret: