Energy crystal
From Wookieepedia, the Star Wars wiki.
The energy crystal was a power source used by the InterGalactic Banking Clan to power their Energy collector core stationed on Mygeeto to power the nearby droid factories. During the Battle of Mygeeto, a detachment of the 501st Legion led by General Ki-Adi Mundi extracted the crystal from the core.
The mission was, in truth, an operation guided by Palpatine known as "Hammertong". The crystal would later be used by Imperial engineers as the energy source for the superlaser of the Galactic Empire's superweapon, the Death Star I.
