A Potted History of the Sith Heirarchy
we know that the Sith carry two. master and apprentice. but wasnt that explained to us in Episode 1. were there any books at all that describe that was how the Sith operated? if there wasnt, then what would have happened if Luke joined Vader? what theory would there have been then?
As for how the Sith operate, there are a number of non-film sources that describe their changing methods over the millennia.
Approximately 5000 years before Episode IV, the Sith rule an entire region of space as a feudal magocracy of sorts. Anyone can grab as much power as they can take and hold, as long as they have enough talent in the Force with which to back it up. There does not seem to be any limit on the number of Sith Lords, though there is only one at a time who may use the title "Dark Lord of the Sith," distinguished by a tattoo on his forehead. A council of about half-a-dozen Sith Lords make decisions, but they spend more time scheming and backstabbing each other than guiding the empire. Following the Great Hyperspace War, in which the Sith Empire is soundly thrashed by the combined forces of the Old Republic, the Jedi, and Empress Teta of Cinnagar, the Dark Lords are wiped out for the next 1000 years. Dark Lord Naga Sadow flees to Yavin 4, where he establishes a sanctuary to plot and preserve the secrets of the Sith. This is chronicled in
Tales of the Jedi: Golden Age of the Sith and
Tales of the Jedi: Fall of the Sith Empire from Dark Horse Comics.
4000 years before Episode IV sees a burst of renewed Sith activity. Small groups of cultists following Sith teachings on Onderon and in the Empress Teta system sieze territory using the Dark Side techniques they discover, plunging the Galaxy ito war once again. There are four known Dark Lords of the Sith in action at this time: Aleema and Satal Keto, who rule the Teta system, and the fallen Jedi Knights Exar Kun and Ulic Qel-Droma. Both Kun and Qel-Drom wore the Dark Lord's distinctive forehead tattoo. They actively sought to recruit apprentices from among the Jedi, especialy Exar Kun. The Royal family of Onderon, while powerful in the Dark Side, did not refer to themselves as Sith Lords. At least one Sith Knight (equal in power to a Jedi Knight but not a full Sith Lord), Warb Null, was known to be operating at this time as well. The majority of the troops serving these Sith Lords, however, notably the mercenary Mandalorian raiders, have no Force training. After their defeat in this conflict, due in no small part to infighting and betrayal among the Sith Lords, the Sith are all but extinguished, with no word of their activity for another 3000 years. The spirit of the slain Exar Kun is imprisoned on Yavin 4, awaiting discovery by students of Luke Skywalker over 4000 years later. This is chronicled in the
Tales of the Jedi series
Knights of the Old Republic, The Freedon Nadd Uprising, Dark Lords of the Sith, and
The Sith War from Dark Horse Comics.
1000 years before Episode IV, an iteresting development occurs in the Sith power structure. At the Battle of Ruusan, a number of Sith Lords, led by Lord Kaan, pit their armies (again, non-Force adepts) against those of the Jedi. Unable to acheive any significant victories due to the selfishness and internal powerplays among the Sith, Kaan uses a "Thought Bomb" which kills all Force users within range, both Jedi and Sith, as a final desperate scorched-earth attack. Only Kaan's second-in-command Darth Bane survives, and taking a confused and frightened young girl from the ranks of the Jedi trainees as an student, he begins the policy of limiting Sith numbers to only Master and Apprentice. This is done not only to prevent the kind of disunity and infighting among multiple Lords that has contributed to every Sith defeat thus far; but also to evade the notice of the Jedi by remaining small and mobile. Bane is also the first to use the title "Darth", which appears to be a contraction of "Dark Lord of the Sith." This is the situation of the Sith until the coming of Palpatine and Darth Maul. This occurs in the
Jedi vs. Sith series from Dark Horse Comics.
In the intervening time, there are other groups of Dark Side adepts which arise, such as the Nightsisters of Dathomir and the Sorcerors of Tund. While not true Sith, the Nightsisters show similar traits. They are organized in a tribal fashion, led by the matriarch Gethzerion. Only women on Dathomir show any Force talent, so membership is exclusively female. While they are more or less an extended family, betrayal and internal strife in pursuit of power are not unheard of, as it has always been with the Sith. Little is known of the Sorcerors of Tund, save that they have been exterminated by one of their number, Rokur Gepta, who sought to gain a monopoly upon their secret knowledge. Clearly, the Sith curse of self-destruction from internecine cutthroat competition held true for them as well.
With the rise of Palpatine, also called Darth Sidious, to the position of Galactic Emperor, the situation changes dramatically. While there are technically still only two Darths, Palpatine allows the existence of a nuber of other Dark Side practitioners. He keeps a circle of advisors at hand called the Prophets of the Dark Side, who specialise in visions and farseeing. Many of the Imperial Inquisitors, whose task was to hunt down Force-talented individuals, display Dark Side training of their own, and some are even fallen Jedi, notably Adalric Brandl. Palpatine even goes so far as to give special training to a number of beings equal to that of a Sith Apprentice, which he calls "The Emperor's Hands." Mara Jade is the most famous, but other known Hands include concubine Roganda Ismarren, High Inquisitor Tremayne, ace TIE pilot Maarek Stele, mercenary bounty hunter Arden Lyn, Vader's protege Lady Lumiya, and the Imperial Intelligence Chief known only by the codename Blackhole. While the Emperor distrusted Gethzerion as a dangerous rival, he successfully kept Dathomir quarantined for years; and it is implied that he had some kind of supporting agreement with Rokur Gepta. Following his death and return through cloning and Sith Consciousness projection techniques, Palpatine is served by about a dozen Dark Side Adepts and gives rudimentary Sith/Dark Side training to his Royal Guardsmen (one of whom, Carnor Jax, will go on to lead the Empire for a brief but violent period) and a unit of Stormtroopers christened "Darktroopers" (not to be confused with the cybernetic soldiers of the same name created by General Mohc a decade earlier), but they do not appear to have much ability in the Force.
The upshot of all this (and getting back to your question, Primetime
😱) is that Palpatine/Darth Sidious had finally managed to keep a relatively large number of Dark Side/Sith Adepts in service to him at once without falling prey to the squabbling that plagued all previous Sith regimes. (Save, of course, for Vader's final act of defiance and Carnor Jax's sabotage of the cloning facility on Byss six years later.) This is partly due to the fact that the Jedi were effectively no longer a concern and the entire Galaxy was open to them; to use an ecological analogy: A species will expand its numbers to take full advanatage of the resources of its habitat in the absence of traditional predators. Secondly, as Dave notes, Palpatine is enough of a master at manipulation that he could easily keep these disparate groups under his command busy watching their own backs rather than casting their eyes to his throne. Thus, if Luke
had actually turned to the Dark Side, it is likely that he would have been absorbed into this group with little effect to the power structure, either at least being inducted into the ranks of the Emperor's Hands or at most replacing Vader as Palpatine's chief go-to guy.
This actually occurs in the
Dark Empire comic series, as Luke gives in to the Cloned Emperor's offer to join him. He does this for two reasons: Luke believes that by learning the Dark Side's methods, it may be possible to use them against the Emperor(He's wrong. It doesn't work that way, as Ulic Qel-Droma learned 4000 years before...); and he hopes that by taking Vader's position, he may come to better understand and eventually forgive his father. Palpatine makes Luke his second-in-command, probably replacing the Dark Side Executor Sedriss, though he is not mentioned at this time. Luke eventually double-crosses Palpatine, as his fall was part of a ploy to defeat the Empire from within. The Emperor claims to have forseen that, but that doesn't help him prevent getting killed again. Frankly, between having left a large chunk of his spirit orbiting Endor as a "psychic bloodstain" marking where the Death Star II was destroyed, and Carnor Jax secretly tampering with the stability of his cloned bodies, Palpatine is just not at the top of his game in the
Dark Empire series. Luke does return to the Light Side, as his love for his friends and family is far stronger than the Dark Side's temptations of power, but he is never quite the same after having felt the Dark Side within him.
As for using the Force to choke the Gamorreans at Jabba's palace, I think that is simply a poor real-life choice on the part of George Lucas, who wanted us to see a mysterious black-cloaked figure and be surprised that it turned out to be Luke. This suspense and misdirection presumably would be achieved by seeing this figure do something terribly out-of-character for Luke. I can't find a reasonable in-story rationale for it.