Belia Darzu ' s fortress On the Deep Core planet of Tython , a hidden fortress was constructed by Belia Darzu , a Dark Lord of the Sith who lived during the New Sith Wars . A square - shaped structure made from black durasteel , the stronghold contained several laboratories where Darzu experimented with Sith alchemy . As a military facility , the fortress featured numerous barracks that housed an army of Sithspawn creatures called technobeast s . Beneath the stronghold was a large underground chamber containing the personal holocron of Belia Darzu . Following the death of Lord Darzu , the fortress remained intact for over two centuries in the absence of its creator . Description . Constructed on the Deep Core planet of Tython , the fortress of Belia Darzu was a square - shaped building measuring 150 meters on each side . Made from black durasteel and used primarily as a military base , the stronghold was surrounded by a thirty - meter high wall . At the front of the fortress were two tower s erected ten meters up from the corners of the exterior wall . Each of these towers harbored an ion cannon operated by an automated defense system . Located on the front exterior wall was the fortress ' s entrance , consisting of a twenty - meter wide gate with no visible handles , hinges , nor a control panel . The entrance of the fortress led into a long hallway , providing access to the rest of the installation . As a military base , the stronghold ' s interior mainly consisted of numerous barracks and mess halls . Further into the structure , however , were a number of laboratories containing a range of equipment and apparatus for Belia Darzu ' s alchemical experiments . Inside some of these labs were sealed beakers resting on top of long metal tables , as well as glass piping lined along the walls . Some rooms contained specimen bottles holding the brains and hearts from a dozen different species , while other labs held notes and sketches following Darzu ' s research . Towards the back of the structure — beyond the laboratories — was a narrow stairway leading into a separate underground level of the fortress . Within this lower level , a long hallway led towards the inner sanctum of Belia Darzu , accessible through a small wooden door . The inner sanctum consisted of a chamber that was around fifty meters long and twenty meters wide , featuring a pedestal in the center of the room holding the holocron of Belia Darzu . History . Sictis Wars . The fortress was constructed by Belia Darzu , a Dark Lord of the Sith who rose to power in 1250 BBY during the New Sith Wars . Choosing the Deep Core world of Tython for the location of the stronghold , Lord Darzu drew upon the power of the dark side that had since become infused into the planet . Within her fortress , the Dark Lord researched the art of Sith alchemy and a Force technique called " mechu - deru " , using her knowledge to create Sithspawn creatures known as technobeast s . Details regarding Sith alchemy , " mechu - deru " and various other topics were recorded in Darzu ' s personal holocron , a device that was stored in the underground inner sanctum of the fortress . The stronghold served as a barracks , housing the Dark Lord ' s technobeast army — the Metanecrons — that was unleashed against the Galactic Republic and Jedi Order during the Sictis Wars . This campaign ended in 1230 BBY when Darzu was assassinated on Tython by the Mecrosa Order , though the fortress nonetheless remained intact and operational for over two centuries after her death . Abandonment . In the aftermath of Darzu ' s fall , the remaining technobeasts continued to inhabit the stronghold and wander its halls . The fortress was otherwise devoid of any lifeforms , lacking even insects or other types of vermin . The holocron of Belia Darzu radiated with dark side energy , causing its power to flow throughout the entire fortress . Attracted by this power , all of the surviving technobeasts made their way towards Belia ' s inner sanctum , congregating around the holocron . By 990 BBY , the location of Darzu ' s fortress had been uncovered by Hetton , a nobleman and a collector of Sith artifacts . This information was eventually divulged to Darth Bane , a survivor of the New Sith Wars who infiltrated Darzu ' s fortress with hopes of finding her holocron . In his attempt to seize the device , Bane was attacked by the remaining technobeasts that lingered within the inner sanctum , forcing him to destroy the creatures . Shortly after Bane retrieved the holocron , he and his apprentice , Darth Zannah , barricaded themselves inside the fortress as they were pursued by a group of five Jedi — Valenthyne Farfalla , Johun Othone , Raskta Lsu , Sarro Xaj , and Worror Dowmat . A lightsaber duel ensued between the group , during which Bane and Zannah managed to kill all five of the Jedi Knights and Masters . Behind the scenes . The fortress of Belia Darzu first appeared in the novel " " , the second adaption of the " Darth Bane " trilogy . In " The Essential Guide to Warfare " , an illustration by artist Chris Scalf depicted the fortress ' s interior .