Impervium was an almost impenetrable alloy known to have been used to coat the hulls of starships.
It was notably used on the hull of Soulless One—the personal starfighter of General Grievous. Although impervium could be penetrated by an en masse barrage of concentrated laser cannon fire, Grievous was never faced with such a show of force while piloting Soulless One, as he was usually aboard his flagship, the Invisible Hand during most battles and engagements. Because of its impervium coating, the fighter made an effective shuttle for the cyborg general, since it could not be easily destroyed.
Lig swords were also made from impervium.