Neutronia

Neutronia was one of the Cybertronian colonies during the Golden Age. It was one of the many planets to be hit by the Rust Plague.

The Covenant of Primus
Mercury led the Mutacons from Neutronia when the Rust Plague claimed the planet.

The AllSpark Almanac
Neutronia was a destroyed planet that was part of both the Autobot Commonwealth and the Quintesson Pan Galactic Co-Prosperity Sphere in the Milky Way.

Ask Vector Prime
In Primax 489.0 Zeta, Neutronia was destroyed by a rampaging Majin Zarak.