"Always two there are: a master and an apprentice." So Master Yoda says of the Sith at the end of Star Wars Episode I: The Phantom Menace. The film establishes that the Dark Lords of the Sith always come in pairs, exemplified in the tense relationship between Darth Vader and Emperor Palpatine. But how was this rule of two established? For the answer to that question, we journey back in Star Wars history to the tale of the Battle of Ruusan, the fall of the Brotherhood of Darkness, and the rise of Darth Bane as told in the mini-series Star Wars: Jedi vs. Sith.
Written by Darko Macan with art by Ramon F. Bachs, inks by Raul Fernandez, colors by Chris Blythe and letters by Steve Dutro, Jedi vs. Sith is set a thousand years before the events of The Phantom Menace. On the planet Ruusan, the war between the Jedi Army of Light and the Sith Brotherhood of Darkness has been raging for a long time. Long enough that the Jedi have been forced to recruit children specifically for the war effort to enlist as padawan apprentice child soldiers. The war has taken its toll on both sides. As a recruiter puts it: "Not everyone serving the dark lords is a monster. Not everyone on our side is a hero."
The story focuses on three children recruited by the order: Tomcat, Rain, and Bug. The three are taken to Ruusan as Force-sensitive soldiers for the Army of Light, but destiny will take them to different places. We are introduced to Darth Bane, a Sith Lord grappling with his growing frustration with what he sees as the wasteful nature of the Sith. As the battle for Ruusan rages, Skere Kaan, leader of the Brotherhood of Darkness, decides to use a dangerous Sith technique called the Thought Bomb in an effort to destroy the Jedi once and for all. When the dust settles only Bane is left alive, and he takes the young girl Rain as his apprentice. He establishes that where once the Sith were many now there will only ever be two. One to serve, the other to rule until the servant slays the master and obtains their own apprentice.
Star Wars: Jedi vs. Sith is one of the darkest tales to be found in the Legends line. The book's existence is owed to a few tantalizing pieces of information provided in The Phantom Menace. The first being Yoda's declaration, the second being a statement from Ki-Adi Mundi declaring the Sith had been "extinct for a millennium." The story is one in which neither side comes out entirely heroic: with battle-hardened Jedi recruiting children (not temple-trained padawans but children) to help them fight the Sith, knowing that the Sith are doing the exact same thing. Pride isn't common to the Sith either, as the Jedi grapple with their own desires to be heroes of legend rather than simply peacekeepers. Long before Rogue One, Jedi vs. Sith was the first Star Wars story to really look at conflict in a galaxy far, far away, but with the added bonus of calling out the Jedi Order and the Sith for their respective toxic effects on galactic peace.
Ironically, the first person to get an inkling of how destructive Force-users can be in the Star Wars galaxy is one of the Sith. Darth Bane realizes that endless legions of self-declared Sith Lords will weaken the dark side as a whole and only allow for further chaos. By implementing the rule of two, there are only two Sith Lords in the galaxy, with greater access to the power and the greater ability to hide. When the Sith moved in vast armies, they made themselves a target. With the Jedi believing the Sith destroyed on Ruusan, it allowed the Sith dynasty to slowly build in power down through the centuries until Darth Sidious was in place to maneuver the Republic into the Clone War and destroy the Sith's ancient enemies in one fell swoop.
The rule of two would later be explored in a series of Darth Bane novels by Drew Karpyshyn, and Bane himself has appeared in Season Six of The Clone Wars (ironically voiced by Mark Hamill). The rule of two is a fascinating piece of Star Wars mythology, and Jedi vs. Sith is a dark tale that sets the stage for the growing menace of the reborn Sith.