Darth Nihilus, shown as a projection from his Sith holocron. The holocron of Darth Nihilus was a Sith holocron created by Darth Nihilus himself.
During the time of the Cold War, the Sith known as Vaverone Zare tried to seize this very artifact at the Lightspring that was located on Tatooine. Simultaneously, the Jedi named Nariel Pridence was trying to stop her from getting the relic.
Eventually, by the year 137 ABY, Darth Krayt came to possess the holocron and then used it to get in touch with the Sith Lord who resided on Korriban.