- "Two there should be; no more, no less. One to embody power, the other to crave it."
- ―Darth Bane
The Rule of Two doctrine, known as Chwayatyun in Sith language and also called the Banite system, was the guiding principle of the Order of the Sith Lords after the internecine New Sith Wars. It replaced the practices of Lord Kaan's Brotherhood of Darkness, which claimed equality among Sith Lords and forbade the use of the title "Darth".
The Rule of Two was instituted by Darth Bane, once a student at Kaan's Sith academy, in response to what he viewed as inevitable, self-destructive infighting within the Sith Order. The Rule of Two states that there would be only two Sith at one time, a Master and an Apprentice, guaranteeing that when the Apprentice becomes powerful enough in the ways of the Dark Side to take the title of Master, only then would they be worthy of the title. This transfer of power would only take place when the Apprentice takes their Master's life and finds a worthy student to repeat the cycle. Both Master and Apprentice were considered to be Sith Lords.
The practice survived with varying levels of enforcement for a thousand years until the murder of Darth Tenebrous at the hands of his apprentice in 67 BBY—Darth Plagueis held the doctrine in contempt, and intended to live forever together with his own apprentice, Darth Sidious. However, Sidious murdered him according to the precepts of the Rule of Two.
- "When your power eclipses mine I will become expendable. This is the Rule of Two: one Master and one apprentice. When you are ready to claim the mantle of Dark Lord as your own, you must do so by eliminating me."
- ―Darth Bane, to Darth Zannah
In an attempt to avoid the seemingly inevitable clash between power hungry Sith, Darth Bane sought to reinvent the Sith Order with only two members—a Sith Master, and an Apprentice. Thus, he utilized the knowledge from the ancient Sith Lord Darth Revan's holocron regarding the concept of the "Rule of Two". Darth Revan was the first to realize the flawed logic of a Sith Lord training more than one apprentice at a time. Bane learned from Revan's holocron that, in times past, students of the dark side who were impatient and hungry for power would make alliances with his Master's other apprentices in order to defeat him and take the mantle of Master.
With no Master to keep the students in line, however, they would eventually turn on each other and kill for the power they had joined to take. In the end, no matter what the outcome, the new Master would still not be as strong as the last one. This process would then continue, leaving an even weaker Master than the previous one at the end of each cycle.
Although Revan's Sith Empire did indeed include a Sith academy and the training of multiple Warriors, Acolytes, and other practitioners, there were only two true Sith Lords—Darth Revan and Darth Malak. In that regard, Revan and Malak somewhat mirrored Exar Kun and Ulic Qel-Droma, although the latter two were more equals rather than master and apprentice; Kun also trained multiple apprentices simultaneously, as well. With this lesson from Darth Revan's Sith Holocron in mind, Bane surmised that he could avoid further intra-Sith conflict by applying Revan's philosophy to the Sith Order as a whole, limiting the Order to only one pairing of master and apprentice.
His course of action decided, Bane destroyed the Brotherhood of Darkness in true Sith fashion by duping Lord Skere Kaan into using a Force technique he learned from his studies of the dark arts known as the Thought bomb. Lord Kaan gathered together every Sith Lord in the Brotherhood as the Jedi were closing in to destroy them when he detonated the Thought bomb. Bane, knowing what would happen to Force-sensitive users within the bomb's range, escaped the Brotherhood's fate and hid from the surviving Jedi. Bane was then free to start his new Sith Order implementing the Rule of Two with his newfound apprentice, Zannah. Through his actions, Bane fulfilled the prophecy of the Sith'ari and ended the New Sith Wars.
For nearly 1,000 years, the Sith watched and waited, destabilizing the Galactic Republic whenever opportunity arose without revealing themselves. Around 188 BBY, during the Dark Jedi Conflict, Kibh Jeen warned the Jedi that the Sith had survived and were operating utilizing the Rule of Two, his warnings were mostly ignored or passed off as the rantings of a madman.
Prelude to the Empire
- "Remember, the first and only reality of the Sith… there can only be two. And you are no longer my apprentice."
- ―Darth Sidious, to Darth Maul
By the time of the Dark Lord Rugess Nome, the Sith had come to the conclusion that the Rule of Two had expired, as the time was coming when they would finally gain their revenge over the hated Jedi Order.
During this 1,000 year period, the Bith Dark Lord of the Sith Darth Tenebrous emerged, taking a Muun, Darth Plagueis as his Sith apprentice. It is noted that Tenebrous broke the Rule of Two whilst training Plagueis, as he took a fellow Bith as an apprentice, dubbing him Darth Venamis. It should be noted that the mantle of Sith Master went to Plagueis, not Venamis. In 67 BBY, Plagueis killed his master on Bal'demnic, taking the title of Dark Lord of the Sith by 60 BBY, seven years later. By then, the Muun had taken the human Palpatine as his apprentice, deciding to call him Darth Sidious. Darth Sidious, under the guise of Senator Palpatine, was elected Supreme Chancellor in 32 BBY and masterminded a devastating galactic war involving the Republic, and, as Emperor of the newly formed Galactic Empire, brought the Galaxy under the control of the Sith, bringing about their foretold revenge.
Sidious broke the Rule of Two at least twice: once by training Darth Maul while still under the tutelage of Darth Plagueis; and secondly, by taking on two apprentices at once, and in the form of two Jedi: Count Dooku, dubbed Darth Tyranus, and the Fosh Jedi Vergere. Vergere was said to be merely a candidate and not a "true" apprentice. It should also be noted that this information derives from Lumiya's account to Jacen Solo, and is the only known source. In Vergere's case however, she left Palpatine's instruction when she left the galaxy with a then unknown extra-galactic scouting party. It also appears that Sidious considered offering Dooku a place at his side prior to Maul's defeat, although details on the timing are vague. Knowing how Darth Sidious drew heavily on the Force to see into the future, these could be considered precautions to ensure that he always had a suitable apprentice even if he did, technically, violate the Rule in its strictest form. In the case of Darth Maul, he had done so with Plagueis' knowledge due to Plagueis having discontinued the Rule of Two by that point, although Sidious reinstated it shortly after murdering Plagueis, reasoning that it was against the very nature of the Sith to not betray the other.
Count Dooku also referred to Asajj Ventress as his apprentice on more than one occasion, though she never became his official Sith apprentice, being abandoned at the Battle of Sullust as per Sidious's orders. Dooku later took Savage Opress as his Sith apprentice, planning to use him to overthrow Sidious and rule the galaxy together, though that plan did not come to fruition either.
Maul broke the Rule of Two, as well, after returning from his exile and uniting with his brother, Opress. Initially, they regarded one another as equals, but after a time Maul demonstrated his superiority and declared himself Opress's master. He remarked that there could only be two—yet in his decision he had created two rival pairs of Sith.
Sidious, Tyranus, and Darth Vader trained and employed a number of Dark Jedi and other Force-sensitive agents such as the Dark Acolytes, the Inquisitorius, and the Dark Side Elite. As these agents were not taught the secrets of the Sith and were considered merely acolytes, not apprentices, they did not consider this a violation of the Rule of Two. However, the fact that Tyranus sought to replace the Jedi Order with a Sith army, the so-called Fist of the Empire, indicated that he had envisioned the abolition of the Rule of Two once the Sith took over the galaxy.
Just as Sidious had taken Darth Maul as an apprentice before truly ascending to the rank of Master, Vader took it upon himself to train a secret apprentice of his own. Due to the sustained injuries that severely diminished his Force potential, Vader was in no condition to successfully challenge his Master, much less kill him. To that end, he endeavored to mentor an exceptionally powerful Force-wielder who would not only serve as his personal assassin, but would one day stand with him to overthrow Sidious. Thus for several years, Galen Marek, codenamed Starkiller, was trained in the ways of the Sith and the Dark side of the Force, thus becoming a merciless assassin who was devoted to the goal of destroying Sidious in order to become a true Sith Lord.
Despite Marek's unanticipated redemption and subsequent death, however, Vader refused to lose an extremely powerful asset and resorted to relying on the cloning technology of Kamino, and thus continued to violate the Rule of Two by creating a clone of Marek to replace his former apprentice. After many failed experiments, including a rogue clone who escaped from the Timira City Cloning Facility, Vader succeeded in achieving his goal by creating a perfect clone who wielded all of Marek's strengths, but none of his weaknesses.
Darth Bane, however, overlooked one possibility—that one of the Sith Lords may be redeemed. When Anakin Skywalker killed Darth Sidious in a selfless act of sacrifice, he redeemed himself of the life he lived as Darth Vader. Without Sidious or Vader, the Order of the Sith Lords was effectively dissolved since its only two members were dead. Thus, it appeared that there were no others to carry on the Order's traditions and teachings, and the Rule of Two was veritably destroyed. Once again, the Sith had destroyed themselves—or so it seemed.
Lumiya, one of Vader's secret apprentices, declared herself Dark Lady of the Sith and established her own Sith Order. She remained faithful to Darth Bane's ancient diktat, the Rule of Two, by taking Flint as her first apprentice, and then Carnor Jax. Her third and final apprentice was Darth Caedus, the grandson of Darth Vader and formerly known as Jacen Solo. Before her death, she instructed Caedus to find an apprentice for himself. He fulfilled her last wish after finding a suitable apprentice in Tahiri Veila, a fallen Jedi Knight whose emotional attachment to Caedus's dead brother brought about her fall to the dark side. However, Caedus's death, alongside Veila's turning back to the light side shortly beforehand, ended up ending the Rule of Two for good.
By the year 130 ABY, a new Sith Order emerged under the leadership of Darth Krayt, thus taking the place of the former Order of the Sith Lords. Unlike Bane's Order, however, Krayt abolished the Rule of Two and replaced it with the Rule of One, with one Dark Lord of the Sith representing the Order itself, while also commanding many Lords, acolytes, and minions.
His revision of the Sith was met with extreme disapproval and outrage, particularly from the gatekeeper of Darth Bane's holocron. When Krayt sought the wisdom of the ancient Sith Lords, they rebuffed him as an offensive heretic and a false Sith. Darth Nihilus did not provide Krayt with helpful information, Darth Andeddu accused him of heresy, and Darth Bane warned the Rule of One would be the death of Krayt and the entire Sith.
Behind the scenes
Chronologically, Darth Rivan predates Darth Bane, yet one of the traps in Darth Rivan's fortress, as shown in A Mon Alone, is based on the Sith adherence to the Rule of Two. However, Rivan did not pre-date Darth Revan, and in fact based his name off of the historical texts of Revan, whose teachings about apprentices inspired Darth Bane to implement the Rule of Two.
On Hypori around 54 BBY, Darth Plagueis said to his apprentice Darth Sidious that rather then the tens of thousands of Jedi, only thirty in a millennium were fit to be Sith, implying that the Rule of Two spanned at least 30 individuals, including or up until him and his apprentice.