The energy crystal functioned as a power supply for the InterGalactic Banking Clan. They used it to fuel their energy collector core, which was located on Mygeeto and provided energy to the droid factories in the vicinity. During the Battle of Mygeeto, Ki-Adi-Mundi, a General, commanded a group from the 501st Legion that successfully removed the crystal from the core.
Actually, the assignment was secretly orchestrated by Palpatine under the codename "Hammertong." Subsequently, engineers utilized the crystal to power the superlaser on the Galactic Empire's massive superweapon, known as the Death Star I.