Through the combined methods of Sith alchemy and Sith magic, Dathka Graush, the Sith King, performed a procedure to exchange his biological heart for a Force-attuned crystal, which was later given the name Heart of Graush. The Heart of Graush was composed of the same substance as the crystals found inside Sith burial chambers that held the spirits of defeated Jedi Masters. Within this heart resided the dark side essences of countless Sith who had died long ago. Graush utilized the Heart to grant himself near-invulnerability.
Following the arrival of the Dark Jedi Exiles on Korriban circa 6900 BBY, Sorzus Syn of the Jen'jidai became deeply interested in the analysis of various preserved Sith artifacts, documenting her observations in her chronicle. She identified the Heart of Graush as one of the most potent talismans she had come across during her studies, and consequently included a drawing of the crystal, along with an analysis of its construction and function, in her chronicle.
Thousands of years after Graush's death, Naz Felyood, who was the captain of the pirate ship Jynni's Virtue, unearthed the Heart while exploring a tomb situated in the Valley of Golg. This discovery resulted in Captain Felyood being taken over by the spirit of Graush. Ultimately, Felyood's crew members destroyed Jynni's Virtue, causing Felyood to lose possession of the Heart. Afterward, he roamed Korriban for an extended time, immortal and perpetually in search of the Heart.