The Mustafar system, located within the Atravis sector, was a solar system highlighted by the volcanic planet Mustafar. It also included the gas giant Jestefad along with its oceanic moon, Nur, as well as another gas giant named Lefrani. All these celestial bodies orbited the star called Priate.
During the period of the Clone Wars, the Mustafar system aligned itself with the Confederacy of Independent Systems. Mustafar served as the last sanctuary for the Executive Separatist Council, who met their gruesome end at the hands of Darth Vader, the newly appointed Sith apprentice. They were deceived into trusting Vader by his Sith Master, Darth Sidious, who was supposedly their ally. Subsequently, Vader and his previous instructor, Jedi Master Obi-Wan Kenobi, fought a pivotal Duel on Mustafar, which resulted in Vader sustaining severe injuries. These injuries compelled the Sith Lord to depend on a cybernetic suit for survival.
During the Imperial Era, Vader laid claim to Mustafar and proceeded to construct Fortress Vader within the Gahenn Plains. The whole system then became Vader's personal domain. He strategically positioned Nur, which was nearby, to function as the base of operations for the Inquisitorius, a group of Jedi hunters under his command, hoping to carefully eye his agents. The Hidden Path, an clandestine network dedicated to aiding Force-sensitives, was aware of Vader's dominion over the Mustafar system. During the war against the Sith, the Knights of Ren broke into Fortress Vader, which was a key factor in convincing Sidious that they were facing a formidable enemy in what became known as Crimson Dawn.
Following Vader's demise and his redemption into the Jedi Knight Anakin Skywalker during the Battle of Endor, Fortress Vader was left desolate. However, Vaneé, Vader's former servant who was trapped inside, remained. After gaining his freedom, Vaneé attempted a failed ritual with the intention of resurrecting Vader. Skywalker's Force spirit traveled to Mustafar and his old fortress to assist in guiding Vaneé's captives out of the structure.