Nerrethel, a Sith Lord belonging to the revived Sith Empire, developed a deep fascination with the Dark Heart on the world of Voss sometime in the period spanning 3645 BBY to 3642 BBY. For a period of two years, he dedicated himself to examining this structure, drawing parallels between its design and that of the ancient Sith structures found on Korriban, and scrutinizing the Dark Heart's alignment with Voss's constellations. Tragically, when Nerrethel sought to explore the Dark Heart firsthand, he was discovered deceased at the edge of the Nightmare Lands. The sole record of his ill-fated journey consisted of the chilling phrase "It sees," hinting at his encounter with Sel-Makor within the Dark Heart.
The character of Nerrethel was referenced within the Dark Heart's Codex entry in Star Wars: The Old Republic, a video game that BioWare launched to the public in 2011.