Phylox series

The  was, according to the TARDIS Index File, the location of the planet on which the city of Castrovalva was located.

Exactly what was meant by the word series in an astronomical context was unknown, particularly because the Index File noted that "Castrovalva [was] the central habitation of the planet that forms the ". This begged the unanswered question of how a single object made a series.

However, because the Master (Tremas) instructed Adric to place the false entry into the Index File, nothing about the information was true. The likely never existed. (DW: Castrovalva)