Metal Planet

The Metal Planet was a star-sized mobile battle station covered in Quantum Armour and was designed to evacuate the entire population of a solar system in the event of a supernova. It had a diameter of about 1.4 million km and took the Galactic Empire two centuries to build. It was built deep in the Cloak of the Sith Region beyond Tatooine, hidden in the D'Anjon Nebula where it would be safe from prying eyes. (Arkanis Sector Grid R-16: SOURCE= D'Anjon Nebula Article on Star Wars Wookiepedia)

It was first proposed to the remnants of the Delegation of 2000 by sympathetic Imperials who opposed Palpatine's slaughter of the Jedi. When the Delegation dissolved, construction secretly began on the Metal Planet.

Under the Galactic Empire
However, the "sympathetic Imperials" betrayed the Delegation members and brought the Metal Planet Project to Palpatine's attention. He secretly dispatched a task force to build it and 20 years later, dispatched a new task force Commander(Andrew) to oversee the construction. Meanwhile, Palpatine built the Death Stars to destroy the Rebel Alliance and if that failed, at least their attention would be focussed on him alone.

By 115 ABY, the Metal Planet was complete and under the Command of Andrew(in cyborg form so he could live to see the destruction of the Yeda Alliance) attacked and occupied the Yeda Rebel Alliance.

Under the Yeda New Republic
But by 116 ABY, the Yeda Rebel Alliance managed to take over the Metal Planet with the help of ACTUALLY sympathetic Imperials who were tired of fighting.

Once Commander Andrew was killed and his forces were defeated, the first act of the Yeda forces with their new base was to evacuate a star system whose sun went supernova. The quantum armour protected the base when the supernova erupted and thus the base had finally fulfilled its intended purpose, instead of being used as a weapon of war.

The Yeda Rebel Alliance renamed itself the Yeda New Republic and for the next few decades the Metal Planet was their main base. Once the Yeda New Republic merged with Stan's forces, the Metal Planet reverted to its first purpose in the time of the Clone Wars: a back-up base for anyone who needed it.

When Stan's United Galactic Empire fell apart in 181 ABY, thanks to the Praxeum and Lok's Galactic Republic(see Star Wars Galaxy Wiki articles at http://swgalaxy.wikia.com/wiki/Galactic_Republic_(Lok) and http://swgalaxy.wikia.com/wiki/Praxeum), the Metal Planet was once again the leadership site for the Yeda New Republic faction. Stan's forces joined them soon after when Mar took over the Empire in a coup (see http://swgalaxy.wikia.com/wiki/Galactic_Empire_(Mar)).