Polymos

Polymos was the home planet of the Nestene Consciousness. It was located at the edge of the Mutter's Spiral galaxy. (PROSE: Doctor Who and the Terror of the Autons)

The Nestene completely infused the planet, destroying all other life on it. It was far from a red star and had surprisingly little tectonic activity. Far in the future, it was invaded by the Time Lords attempting to stop the plastic asteroids from leaving. (PROSE: Synthespians™)

The Darksmith Collective salvaged plastics from Polymos' wreckage in the 28th century to build the robot called the Agent. (PROSE: The Dust of Ages)

The planet was destroyed during the Last Great Time War.