Sith cave An ancient Sith cave was located on the Outer Rim Territories planet Mustafar , which housed a locus for the dark side of the Force deep beneath its volcanic surface . The cave resided in the course of one of the planet ' s lava rivers and was strong with dark side energy . Shortly after the rise of the Galactic Empire , the newly - christened Sith Lord Darth Vader traveled to the Sith cave to use its energy to " bleed " a kyber crystal in the construction of his own lightsaber . Vader later built a castle over the cave to channel the power of the dark side and serve as his personal residence . Description . An ancient Sith cave was located on the volcanic Outer Rim Territories planet Mustafar , which housed a locus for the dark side of the Force deep beneath its surface . The cave resided in the course of a fiery river of lava , which flowed through and dropped out of the cave as a lava fall . The cave ' s interior featured various markings on its walls , as well as a round rock table naturally formed at its center . History . Shortly after the formation of the Galactic Empire in the year 19 BBY , the Sith Lord Darth Sidious ordered his newly - christened apprentice , Darth Vader , to steal a Jedi ' s lightsaber in order to construct one of his own . After obtaining Jedi Master Kirak Infil ' a ' s lightsaber , Vader , again following his Master ' s orders , traveled to Mustafar , where he had previously suffered severe burns all over his body as a result of his lightsaber duel against his old Jedi Master , Obi - Wan Kenobi . To complete the task of constructing his new lightsaber , Vader needed to draw upon the Sith cave ' s dark energy and " bleed " the stolen lightsaber ' s green kyber crystal — corrupting the crystal with the power of the dark side and turning its color to red in the process . After Vader placed the crystal on the cave ' s rock table , the markings on the walls began to glow as he experienced a Force vision in which he denounced the dark side , killed Darth Sidious , and returned to Kenobi ' s side . By re - embracing the darkness , Vader escaped the vision and finally bled the kyber crystal . By 5 BBY , Vader had constructed his own castle over the Sith cave , which was also once the site of an ancient castle full of dark secrets . The massive obsidian tower was designed to channel the power of the dark side of the Force — it was divided in the middle to resemble tuning fork s and harnessed Mustafar lava for energy . Behind the scenes . The Sith cave was created as part of the backstory for Darth Vader ' s castle , which was designed for " " , the first film in the " Star Wars Anthology Series " . The cave was first mentioned in " " , published on December 16 , 2016 , the same day as the film itself . The Sith cave made its first canon ical appearance in the comic book " " , written by Charles Soule with art by Giuseppe Camuncoli , and released by Marvel Comics on September 6 , 2017 . According to Doug Chiang , co - production designer for " Rogue One " , the idea of a Sith cave beneath Darth Vader ' s castle originated from a piece of Ralph McQuarrie concept art of Emperor Palpatine ' s throne room created for . Chiang found the image of the throne on a lava lake inside a cave compelling and decided that the castle would be built on the foundation of an ancient structure . He intended to give the castle ' s final design an element of purpose , which was to draw energy from the lava lake much like a dam . Furthermore , Chiang thought that the castle could have a more ancient part below it , in the form of a natural cave where Vader went to meditate . Although the StarWars . com Databank entry for " Darth Vader " explicitly states that Darth Vader ' s castle was built over an " ancient Sith cave , " the 2016 reference book " " states that it was built over an " ancient castle full of dark secrets . " Although this is an ostensible continuity inconsistency , the Lucasfilm Story Group ' s Pablo Hidalgo , the book ' s author , clarified that " it depends how deep you dig . "