Bast Castle, situated on the acid rain-soaked planet of Vjun, served as the secluded stronghold for Darth Vader—the Dark Lord of the Sith and Supreme Commander of the Imperial Forces. This was his personal fortress. In the time following Vader's passing, the Dark Side Elite took over the castle, using it as their base of operations, led by Dark Jedi such as Sedriss QL and, subsequently, Xecr Nist.
Located near a beach on Vjun, Bast Castle was a massive black fortress that functioned as the secret retreat of Darth Vader, who was the secondary commander-in-chief of the Imperial Forces. The Lord Vader, making it his private residence, would often withdraw to Bast when he was not actively serving the Emperor. Its existence was known to very few sentients, and it was here, in isolation, that he dedicated himself to studying the dark side and trying to discover the means to mend his damaged body, frequently utilizing his personal meditation chamber which was positioned at the summit of the bastion. When he wasn't immersed in the dark side, the Dark Lord devoted available time to refining his lightsaber skills, employing various types of training droids to provide challenging practice. The castle also housed a droid workshop and a private hangar, where Vader applied the mechanical skills he had acquired during his time as a slave to personally maintain his TIE Advanced X1 and repair his sparring droids. Vader also once tortured a Toydarian to death within its walls. Besides the Dark Lord, the castle was manned by a garrison of Stormtroopers, who were stationed both inside the castle and at surrounding outposts. These troopers were tasked with safeguarding Bast Castle during Vader's absences, when he was fulfilling his duties or on assignments for Palpatine. The fortress was not the only stronghold available to the Dark Lord; a public palace also awaited him at the Imperial Centre, also known as Coruscant, close to the Emperor's own residence. Following the death of both rulers, the fortress remained unoccupied and forgotten for a number of years.
After the Battle of Endor, the former clone trooper designated X1 made the decision to establish a new empire, with himself as its ruler. Proclaiming himself a Sith Lord, he aimed to harness the power of the dark side. However, lacking the necessary knowledge of the Sith, he journeyed to Vjun to find a holocron located within Bast Castle. His brother, X2, also went to the fortress in an attempt to stop him, but by the time he arrived, he discovered that his clone brother had already left for the volcanic planet of Mustafar.
Before the Emperor Palpatine's return in another clone body, Bast Castle was taken over as the headquarters of the Dark Side Elite by the Dark Jedi Sedriss QL, who was presented as a subordinate replacement for the deceased Lord Vader. To pay tribute to the fortress's previous occupant, Sedriss had a statue of Vader constructed. After Palpatine's resurrection, the reborn Emperor interrogated and tortured inexperienced Ysanna Jedi within Bast Castle, under the watchful gaze of a large statue of his former apprentice. When Luke Skywalker and Kam Solusar launched an assault on the citadel to rescue the Ysanna, it sustained significant damage during the battle, and Vader's statue was knocked over, crushing several of the Dark Jedi underneath.
In 14 ABY, Jedi Master Kyle Katarn and his Padawan Jaden Korr traveled to Vjun and visited the castle in an attempt to prevent the Disciples of Ragnos from draining its Force energy. It was at this time that Rosh Penin revealed his turn to the dark side. Before encountering Penin, Korr noticed the fallen statue of Vader and jokingly remarked to himself that someone clearly had a strong dislike for the warlord. Korr ultimately defeated Penin and eliminated the Kothos twins who had accompanied Penin and empowered him with the Force.
Later, in 22 ABY, Tionne Solusar, a Jedi historian, discovered that Obi-Wan Kenobi's lightsaber had been retrieved by the Sith Lord Darth Vader and kept at Bast Castle. Due to the fact that an information broker had sold them this information, she was concerned that others might have reached it before them. Thinking it was a simple mission and a good opportunity for training, Tionne permitted Anakin Solo, Tahiri Veila, Uldir Lochett, and Ikrit to accompany her. They departed on her Jemlaat-class yacht named Lore Seeker.
Upon their arrival at Bast Castle, they spotted another ship and worried that another group had gotten there ahead of them. After surviving the fortress's automated defenses and booby traps, they located the lightsaber in a hidden alcove. Unfortunately, a cloaked figure named Orloc appeared. Orloc stole Kenobi's lightsaber and professed to be a mage with significant powers.
In response, the Jedi chased Orloc and his followers through Bast Castle. They succeeded in defeating Orloc and escaping Vader's old fortress, taking with them Kenobi's lightsaber and the holocron of the ancient Jedi Master Asli Krimsan.
Following the demise of its initial owner, Bast Castle transitioned into the base of operations for the Emperor's Dark Jedi. As a gesture of respect to the Supreme Commander of Imperial Forces and Dark Lord of the Sith, whose position as the new Military Executor he had inherited, Sedriss QL commissioned the construction of a Darth Vader statue in the heart of Bast Castle. Sculpted from black stone, it stood approximately 6 meters in height. Palpatine demanded that the likeness of his treacherous apprentice be destroyed, but Sedriss disregarded this command out of admiration for Vader's capabilities.
Sedriss was eventually killed by Ood Bnar, and the ownership of the castle passed to the new Executor, Xecr Nist. Palpatine reiterated his order for the statue's removal, and Nist, eager to avoid his predecessor's fate, pledged to comply, although he also hesitated to demolish the idol of Darth Vader. However, before the task could be carried out, a Jedi task force, including Luke Skywalker, Rayf Ysanna, Kam Solusar, and Empatojayos Brand, attacked the stronghold. A fierce battle ensued between the four Jedi and the Dark Side Elite.
In a twist of fate, Skywalker defeated Nist and used the Force to topple the massive statue onto the remaining Dark Side Elite, eliminating them and securing victory for the Jedi. The statue remained broken within Bast Castle for years, and its remnants were still visible when Kyle Katarn and his student Jaden Korr visited the planet in an attempt to prevent the Disciples of Ragnos from draining the Force energy. Anakin Solo and Tahiri also toured the castle during their training at the Jedi Praxeum and observed the remains of the imposing statue.
Bast Castle was protected by an intricate network of staffed defenses that extended several kilometers into the surrounding ravines. It also featured at least one turbolaser turret. The facility also housed a number of ASP-38 Droids whose purpose was to eliminate any intruders, though many of these were destroyed by X2.
During Jaden Korr and Kyle Katarn's mission to Vjun, a pair of TIE/sa bombers executed strafing runs across a valley and the castle's entrance. A starfighter hangar was positioned on the upper levels, containing two inactive TIE/LN starfighters along with Vader's personal TIE Advanced x1. Later in their mission, they came across several locked doors that were resistant to lightsabers. The two Jedi traversed the castle's extensive shield generation facility, navigating through multiple control rooms and causing the collapse of the power column room, which allowed them to access the Upper Castle.
The castle seemed to have a substantial garrison of stormtroopers, many of whom were equipped as rocket troopers or hazard stormtroopers, in addition to numerous E-Web Emplacements. Based on ruins discovered by Jaden Korr, AT-ST walkers were likely stationed at Bast Castle at some point.
Early conceptual artwork for Star Wars: Episode V The Empire Strikes Back included a sketch by Ralph McQuarrie that depicted the intended design for Vader's castle.