Malachor III, a planet situated within the Malachor system, resided in the Outer Rim territories.
Well before both the Cold War and the Mandalorian Wars, Malachor III held membership in the Sith Empire. It served as the final resting place for Terrak Morrhage, a Human male Sith Lord belonging to the revitalized Sith Empire, who had perished centuries prior to the Cold War. His spectral essence lay dormant until a Jedi exploration team, consisting of Parkanas Tark, Yuon Par, Duras Fain, Sidonie Garen, Eriz Vossan, and Cin Tykan, inadvertently roused it. Morrhage's spirit manipulated the feelings of the youthful Jedi, ultimately leading to their madness. After fleeing the world, these Jedi informed the Jedi Council of what they found, resulting in the planet being officially labeled as "barren."
Following his presumed elimination of Darth Zash's apprentice, Darth Thanaton journeyed to Malachor III, where he had matters requiring his attention.