"Always two there are.  No more, no less.  A master and an apprentice." - Yoda

"Fear.  Fear attracts the fearful, the weak.  Fear is my ally." - Darth Maul "One of the themes throughout the films is that the Sith lords, when they started out thousands of years ago, embraced the dark side.  They were greedy and self centered and they all wanted to take over, so they killed each other.  Eventually there was only one left and that one took on an apprentice.  And for thousands of years, the master would teach the apprentice, the master would die, the apprentice would then teach another apprentice, become the master, and so on.  But there could never be more than two of them, because if there were, they would try to get rid of the leader, which is exactly what Vader was trying to do, and that's exactly what the Emperor was trying to do.  The Emperor was trying to get rid of Vader, and Vader was trying to get rid of the Emperor.  And that is the antithesis of a symbiotic relationship, in which if you do that, you become cancer, and you eventually kill the host, and everything dies." - George Lucas "During one of his lessons, a young PADAWAN-JEDI, a boy named Darklighter, came to know the evil side of the Force, and fell victim to the spell of the dark side.  He ran away from his instructor and taught the evil ways of the dark side of the Force to a clan of Sith pirates, who then spread untold misery throughout the systems.  They became the personal bodyguards of the Emperor. "The Jedi were hunted down by these deadly Sith knights.  With every Jedi death, the dark side grows more powerful. "Now, the Jedi are hidden; but many are still fighting to free the systems from the grip of the Empire..." From The ADVENTURES OF THE STARKILLER EPISODE ONE: THE STAR WARS, by George Lucas, 1975