Nestenia

Nestenia was the Crownworld of the Nestene Consciousness and a part of its Plastic Conjunction. The planet was destroyed during the Last Great Time War. The Nestene vividly remembered the day it fell. (PROSE: Revenge of the Nestene)

Behind the scenes
Nestenia
 * Due to the name, Nestenia was obviously intended to be the home planet of the Nestene, or at least a colony of some sort. However, this is never stated or even alluded to in-universe. Additionally, multiple other in-universe sources give the name of the Nestene’s home world as Polymos. One thing that is concurred on by all sources is the destruction of the planet during the Time War. (TV: Rose, PROSE: Natural Regression, A Brief History of Time Lords, Rose, WC: Revenge of the Nestene)