Five Planets

The Five Planets were several worlds referred to in passing. Maren of the Sisterhood of Karn stated that no ship could enter the Five Planets without the Sisters knowing, presumably referring to Karn itself and the neighbouring planets in Kasterborous. (TV: The Brain of Morbius)

In relation to the Sirius system, Morgus was said to be the richest man in the Five Planets. (TV: The Caves of Androzani)