Warworld (planet)

Debut - DC Comics Presents #27 (Nov 1980)
Creator/s - Len Wein, Jim Starlin
Species - Originally the Warzoons, later the Largas, last known species were the Martians.
Space Sector - (Variable)
Star System - Sol (formerly Cygnus)
Heroes From This Planet - (none known)
Villains From This Planet - (pretty much every Warzoon was evil)
Attributes Of This Species - (none known)
Attributes Of This Planet - Extensive array of weapons
Other Notes - This planet was destroyed and has not appeared in the New 52 reboot.

Created by the alien race known as the Warzoons, Warworld is an artificially made planet which was originally a satellite but then was modified into a planet-sized weapon which can be flown through space like a ship. The entire planet including all of its weapons can be controlled telepathically by anyone sitting in the control chair. Among other things, Warworld possesses laser cannons and nuclear missiles which are easily capable of obliterating entire planets.
The Warzoons were a barbaric species who spread destruction throughout the universe but they inexplicably died out and the last of them was found inside the Warworld Satellite at its controls. The alien who found the last Warzoon was a Largas. The Largas were a peaceful species and could not bear to be destructive and destroy Warworld so instead they used the planet's crystal key to shut it down. They kept the key safe for a long time but eventually they too began to die out and the last of the Largas race gave the key to the Martians for safekeeping.
Later, the super-villain Mongul captured the crystal key and activated Warworld as part of his plan to take over the universe. Superman and Supergirl both went to stop him but with Mongul at the control chair, giving him power over the entire planet, it was too much for even them. Then they realized that the reason the Warzoons had died out was that the control chair put too much strain on their brains. Superman and Supergirl then created a situation where Mongul had to telepathically control all the planets weapons at once, putting immense strain on his brain and he was forced to give in. Superman and Supergirl then broke into Warworld and destroyed it, ending any potential threat.