The office of Controller began in the Forts with the person who had responsibility for keeping the schedule board for channels. This was sometimes a Gen but often a renSime. The best channel in the Fort worked with the schedule keeper to decide which channels worked for and with which renSimes and Gens and when transfers had to be slotted into the schedule.
After Unity, the function of keeping a schedule board and making judgement calls about individual requirements, matching channels with Donors and the working channel/Donor pair with tasks became spread of wider and wider geographical regions. The process had to be formalized.
The necessity for communication drove the invention of every sort of technological communications method. Sime Territory got to the digital phone system before Gen Territory for that reason, and because Sime mentality and culture tended to focus on small details while Gens thought and worked in large scale engineering.
With communication, Regions grew larger, selyn collection and distribution grew more efficient and reliable, and the job of Controller became more crucial. Authority centralized in the Controllers, eventually creating the office of World Controller.
The Controllers had the full responsibility for managing the entire Tecton staff under them, a bureaucracy developed to collect and distribute selyn. When selyn powered technology became the basis of civilization, this office became the most crucial, most political, and most powerful of offices. It is a job that can only be done by a channel, one able to zlin and judge selyn fields with high precision, but no channel of sufficient caliber to do the job well really likes the Controller's job because it takes time away from channeling.
The Controller's job is an administrative, paper-pusher's job more suited to an accountant's mentality than to that of a physician or Healer, which is what channels are shaped into by Tecton training. Yet only a channel can be trusted with the judgement calls a Controller must make.
As the career path of Controller formed, it attracted channels who weren't, by personality or talent, suited to the job of Healer, channels like Mickland in Unto Zeor, Forever, and more competent individuals who simply disliked patient-care.