If you ask a casual fan of the Star Wars franchise, what the Sith is/are, they'll likely say that they are the bad guys of the series and follow the dark side of the force. While this is true, it is a gross over-simplification of one of the most iconic groups of bad guys the world of science fiction has ever known.
If we base our knowledge purely on canon (the movies, the television series' and anything Disney has produced since the acquisition), there is only so much to work with in terms of learning about the Sith. For a long time, it was the expanded universe that allowed fans greater understanding about this ancient, evil ideology. The expanded universe was of course re-branded as "Legends" by Disney, and declared not to be canon, but this declaration is somewhat meaningless to many fans, and the expanded universe may not be official but it is still an awesome series of adventures that add to and enhance the body of work that is considered canon.
As Disney continues to add to the story of Star Wars, they will likely add to and modify the history of the Sith. However, as it stands right now, there is a wealth of information in the expanded universe that makes the story of the Sith an intriguing and frightening one. With that said however, the evil faction in the series remains an enigmatic one: here are fifteen things you likely didn't know about the Sith.
15 Darth Bane and the "Rule of Two"
Darth Bane, a Sith Lord from about a thousand years before the Battle of Yavin (Episode Four), is credited with having codified the main rule for Sith rulership as "The Rule of Two". While the Sith would embody more than two people, and include minions and officers, the leadership at the very top would be comprised of two people: a master to hold power and an apprentice to crave that power. When the apprentice was able, he or she was to kill the master: the goal of this tradition was to keep the strongest person at the top and the Sith always becoming stronger.
This rule was commonplace among early Sith, but for some time before Bane they had fallen away from it. The theme of apprentices eventually overtaking their masters is a regular one throughout the expanded universe and a central aspect to the culture of the Sith in most of the series.
14 Palpatine, Krayt and the "Rule of One"
The Rule of One is a recent development in the history of the Sith, and replaced the Rule of Two. For the purposes of the Rule of One, it means that there should be one leader in charge of the Sith. This rule stressed discipline and obedience to one person and was practiced by Darth Sidious and Darth Krayt, who came after him. This doctrine goes against the entire history of the Sith, but was supported by a prophecy that said there would come a Sith so powerful he would not be in need of replacement.
13 The Term Darth
The word "Darth" has no definitive meaning, but some have suggested it comes from ancient Rakatan (Rakata were one of the first races conquered by the Sith, long ago) words such as "emperor", or "immortal", but this is a flawed theory. Nobody really knows the etymology of the word.
For our purposes however, it is an ancient symbolic title which demonstrates power and achievement within the Sith religion. It can be used with a person's original given name but most Sith lords choose to abandon their birth names and take a Sith name; Maul, Vader, Sidious, Bane, and so on. "Darth" was abandoned for some time by the Sith, because it was believed that open use of the title made them easy targets for Jedi.
12 Their Unique Powers
There are certain force powers we all know, such as push, pull, mind manipulation, precognition, healing and incredible reflexes, but within the expanded universe there are a multitude more skills and many of them belong exclusively to the dark side and the Sith. Obviously choke and lightening are well-known from the films, but Sith can also use their hate to channel energy and turn it into weapons. Sith can create dark side animals to fight on their behalf, Sith can use the force to cloud the judgment of their enemies (like Sidious did to the Jedi Council), and some Sith Lords have created ways (including diseases) that actually turn their foes into their slaves. Even necromancy and possession by spirits are skills that Sith can learn; there is almost no limit to what they can do through the force.
11 Not All Sith Use Red Lightsabers
It is a misconception that all Sith use red lightsabers and Jedi are unwilling to use that color. Jedi Master Adi Gallia used a red saber briefly and there are a couple of Sith who have opted for other colors, including Darth Vader, who stuck with blue until after the events of Revenge of the Sith and ancient Sith Lord Exar Kun, who also stuck with his blue blade. The primary reason that Sith end up with red lightsabers used to be that they were forced to use synthetic crystals (which always result in a red blade) because Jedi control the worlds on which Kyber crystals are found.
Disney decided that they'd change this and now there is a new reason for the red blades. The (sarcastic) geniuses at Disney have decreed that the only way Sith can get their hands on Kyber crystals is by killing Jedi, and thus, when they do, they don't have a connection to the crystal (Jedi have a connection to their crystal when they build their weapon), and must make it adhere to their will, causing the crystal to "bleed" resulting in a red blade.
Disney probably didn't need to touch this one, but alas, they have the rights to the franchise; they'll do what they want.
10 But Regarding Those Sith Lightsabers...
Whether you like either of the reasons for the red blades, there are some interesting facts regarding the lightsabers of the Sith. The Sith are actually credited, in the expanded universe, with having invented the technology that led to the invention of the lightsaber as we know it. Thousands of years before the days of The Old Republic, the Forcesaber was a weapon of the Rakatan, then a race affiliated with the Sith. The Sith have also opted not only for double bladed sabers, but also for sabers with shaped hilts, such as the curved hilt of Count Dooku's weapon. These modifications, along with others such as the spinning mechanism used by the Inquisitor (in Star Wars: Rebels) are all Sith ideas and inventions.
9 Finally, Do They Even Need Lightsabers?
In the Star Wars universe it is a common idea that there is no better weapon than a lightsaber in the hands of a trained user. One of the most well-known Sith Lords in the series however, considered the weapon a thing of the past, unnecessary for the Sith. Lord Sidious has said that the lightsaber is something that Sith continue to use only because being defeated by it is humiliating for his Jedi victims. While Palpatine (Sidious) carried a lightsaber and was a gifted swordsman (making a few Jedi look like fools and going toe-to-toe with Yoda), it is likely that he carried and used it only for the sake of mocking his victims. The Emperor's views on lightsabers are primarily drawn from the novel Dark Lord: The Rise of Darth Vader, which details Anakin's dark side training after the events of Revenge of the Sith.
8 Use of Holocrons
One of the oldest and most important of Sith traditions is the use of holocrons to keep and pass along information. Jedi have used the similar technology for millennia and while the Jedi holocrons were usually square, the Sith equivalent have mostly been pyramid shaped. They require dark side energy to activate and can be very difficult to access by users of the light side given that they often give off waves of dark energy, affecting everyone in the vicinity. The tradition of Sith using holocrons to store information goes all the way back to the early days of the Sith, when they created them when they started working with the Rakata during their early expansion throughout the galaxy.
Some holocrons can teach new techniques while others simply hold historical information. Either way, they are immensely important to the ideology.
7 Homeworld: Korriban or Moraband?
There is some disagreement over the real name of the Sith home-world. In the expanded universe/legends series it has been Korriban, but Disney and George Lucas have said that the planet will be called Moraband. The names refer to the same place, but the current canon says that Moraband is the modern name and Korriban was used in the past.
No matter what you call it, it is a warm, desolate, unpleasant place. Whether or not the sun is shining, it is dark, and dreary, with little if anything in the way of vegetation. It looks like the kind of place in which the dark side of the force would thrive. The animals that do live on the planet are vicious and terrifying and there isn't much of note on the planet beyond the Valley of the Dark Lords and the Sith Academy.
6 The Forgotten Homeworld of the Sith
Millennia before the Clone Wars and the days of the Empire, there was massive infighting among the Sith (a pattern that almost defines their ideology), and many of them eventually fled Korriban (Moraband, whatever) and found new homes. The former homeworld was left as an area more or less inhabited by the religious fanatics of the Sith, while most of the rest made their way to a world known as Ziost. Of course, there is some inconsistencies and the expanded universe has not made up its mind conclusively whether or not the Sith originated or Ziost or Korriban, although Korriban is the better known of the two planets known as the Sith home-world. Ziost also served as an imperial capital for the Sith over the course of several periods of expansion throughout their history. Over time, Ziot came to look more and more like Korriban with little vegetation; little more than a miserable wasteland.
5 The Sith Code
The Jedi have a code which basically entails their entire belief system and their mission. The Jedi Code reads as follows: "There is no emotion, there is peace. There is no ignorance, there is knowledge. There is no passion, there is serenity. There is no chaos, there is harmony. There is no death, there is the Force." This is all pretty self-explanatory, and present the Jedi as masters of self-control and defenders of peace.
The Sith Code takes a very different tone. "Peace is a lie, there is only passion. Through passion, I gain strength. Through strength, I gain power. Through power, I gain victory. Through victory, my chains are broken. The Force shall free me." From their code, we can see that why the Sith are the way they are. They view the Force as something to be dominated and used, while the Jedi see it as something that must be respected and treated with reverence. The Sith Code also demonstrates a longing to prove oneself to be superior, while the Jedi Code stresses the necessity of self discipline.
4 Sith or Dark Jedi?
This won't surprise most dedicated Star Wars fans but we'll list it all the same for the casual enthusiasts.
Not all Dark Jedi are considered Sith and conversely, not all Sith are Dark Jedi. In short, the two designations are not one and the same by any means. Many Dark Jedi are Sith and many Sith are former Jedi who now follow the teachings of the Dark Side of the Force but one does not imply the other. A Dark Jedi is simply a force user who no longer ascribes to the Light Side and uses his power for his or her own gain, violating the Jedi Code. A Dark Jedi does not need to be trained by the Jedi however, and can learn the ways of the Dark Side through anyone and does not have to be affiliated with any organized group. The "Sith" as we have come to know them refer to those who follow the Code of the Sith and ascribe to the religion and belief system. Of course, Sith were not always a sect, they were originally...
3 They Were Originally A Species
Long before they were the religious fanatic warlords rampaging across the galaxy laying waste to everything in their path, the Sith were a species of red-skinned humanoid race. Some call them "Purebloods" or "Red Sith", and after exiled Dark Jedi landed on Korriban about seven millennia before the events of A New Hope, the Sith species gradually interbred with humans, which essentially got rid of the race and replacing them with human-Sith hybrids.
Sith society was caste-based, violent and barbaric, and in spite of these beings constantly being in conflict with each other, they did at one point have an empire that spanned over much of the galaxy. They were force users and favored the Dark Side. Many of the aspects of ancient Sith culture are the building blocks on which the Sith religion has been based.
2 The Sith'ari
Long ago (even by Star Wars standards, like 27,000 Before the Battle of Yavin), when Sith were still a species, there was King Adas, a leader so powerful that many thought he was invincible. He was also the first Sith to learn the use of holocrons that we mentioned earlier. He reigned as the king of Korriban for centuries, unified the planet under his leadership, and gained a legendary reputation during his later life. His people began to call him "Sith'ari" which is loosely translated to "overlord". This became a common theme throughout the history of the Sith, and a prophecy after Adas' death: a perfect Sith being, who would destroy the Sith as they were, and build them up more powerful than they were before. Some notable Star Wars figures thought to be potential Sith'ari include Darth Plagueis, Darth Bane, and Darth Sidious. This prophecy is similar to the Jedi prophecy of the Chosen One, but the Sith'ari is looked upon as closer to a God-figure.
1 They Have Been "Extinct" or Near-Extinct A Few Times
Technically the Sith species is considered extinct. They were, like we said, interbred with humans over a long period of time until they were all but wiped out. While there may still be people in the Star Wars universe in the time of the Empire with some Sith blood in their veins, it is incredibly diluted, thousands of years worth of dilution in fact.
While the real Sith have been extinct for a long time, the ideological Sith have come near to extinction many times, and have always come back. In Episode One: The Phantom Menace, we witness the fact that the Sith were considered extinct, but came back with a vengeance. Darth Maul attacking Qui Gon Jinn revealed their renewed presence in the galaxy. We all know where it went from there.
But realistically (come on, Jedi would be smarter than this in reality) nobody should use the words "Sith" and "extinct" in the same sentence unless referring to the species. For thousands of years prior to the prequel trilogy, the Sith were an ideology: you can't kill an ideology. Many times, the Sith have driven themselves to the brink of oblivion and other times, the Jedi have put them there, but like we said, it is impossible to kill a set of ideals. The Sith as they exist in the Star Wars films cannot go extinct.