Collier is a planet which was once part of the Divine Principality. A rebellion by agricultural workers, supported by the Farmer, led to the kidnapping of the child Princept. Eventually they were retrieved; in retribution the planet was cut off from the Principality's Portcullis system, erased from its maps, and the people there were left to fend for themselves.
Thisbe woke up here and worked with the farmers who found her until she was taken by pirates.
After Millennium Break begins spreading through the galaxy, they establish a central base on Collier.