Seoularian crystals.

Seoularian crystals were a type of crystal native to the planet Seoul 5. They were a source of power, and after being stockpiled in a crystal control room, they helped power the main city on the planet. The crystals were unique in that they responded to mental power, and were able to create concentrated shock-waves strong enough to knock someone off their feet. A key crystal could be used to control all the other crystals. After the Battle of Endor, Imperials under the command of Captain Drezzel visited Seoul 5 to investigate the possibility of using the Seoularian crystals as new weapons. However, Han Solo, who had come into possession of the Key crystal, thwarted the Imperial's efforts by destroying Seoul 5 city and the crystal control room. Although the destruction signified the loss of a major archaeological find, it also destroyed the only known cache of Seoularian crystals, preventing the Imperials from using the crystals as weapons.