Paradron is an Autobot colonial planet hidden away from the wars that plagued Cybertron. Paradron's was a democratic society, founded long ago by ancient Autobots who believed that fighting only begets more fighting.
The energon-rich Paradron bore a resemblance to Cybertron during its golden age. The planet seemed to be a rocky world which was almost entirely built over with Cybertronian city-structures. Paradron had an unlimited supply of Energon, which made it a tempting target to the Decepticons. The source of this power was a kind of energon pool or lake located at the planet's core. This glowing reserve was processed by a convertor or pump or something -- a big doohickey, basically.
Paradron no longer exists. Rodimus Prime ordered it destroyed to keep it from fueling the Decepticon empire. Harsh.
Paradron was a lost Autobot colony accessible through a space vortex. It was discovered when Cyclonus and Scourge fled through the vortex from the Aerialbots. Upon arriving, the Decepticons found that the Autobots which inhabited the planet were wimpy pacifists 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 world falling into the hands of the Decepticons, the planet was evacuated and Rodimus Prime ordered Ultra Magnus to detonate Paradron's energon core, destroying it.
The survivors of Paradron were relocated to Cybertron, where Rodimus Prime hoped that they would learn that their freedoms had to be defended in order to be kept.