Paradron

Paradron is one of the 13 Autobot colonies, and an energy-rich paradise hidden away from the wars that plagued Cybertron.

Animated Series
In the Generation 1 cartoon, Paradron was a lost autobot colony hidden through a black-hole. It was discovered when Cyclonus and Scourge fled through the hole from the Aerialbots. Upon arriving, the Decepticons found that the Autobots which inhabited the planet were complete pacifists of the worst sort, and easily conquered them.

Enslaved by the Decepticons, a handful of Paradron's Autobots, led by Sandstorm contacted Cybertron looking for help. The Autobots under the command of Rodimus Prime sought to liberate the planet, but found it impossible to retake. Rather than risk such an energy-rich plant falling into the hands of the Decepticons, the planet was evacuated and Ultra Magnus detonated it's energon core, and destroyed it.

The survivors of Paradron were relocated to Cybertron, where Rodimus Prime hoped that the Autobots taken in would learn that their freedoms and paradise had to be defended in order to be kept.

Unicron Trilogy
The existance of Paradron in the Unicron Trilogy, in Japan, is heavily hinted at by the appearance of the Japense exclusive 'Paradron Medic', a green repaint of the Energon Arcee figure.

Though this version of Paradron was never conquered by the Decepticons, it's also not one of the main Autobot colonies, and apparently lacks a cyber-key of its own. The continued existance of the colony remains secret, even from most Autobots.