For centuries, the group of philosophers that would eventually become the Jedi contemplated the mysteries of the energy field known as the Force. Eventually, some of the group's members mastered the Force. After that, they dedicated themselves to using their new-found skills and powers for good, helping those in need.
In the thousands of years that followed, the Jedi served as protectors of the Galactic Republic. Answering to their own Jedi Council and operating in concordance with the Judicial Department of the Office of the Supreme Chancellor, the Jedi became the guardians of peace and justice in the galaxy.
Their deeds became famous. Aided by the Force and armed with their unique lightsabers, they came to be respected and honored throughout the galaxy. They were known as scholars, warriors, and philosophers. They were all those things—and much more. The Jedi spread across the galaxy, protecting the Republic and watching over its many systems.
However, within their knowledge lay the seeds of their destruction. Early on, the Jedi realized the differences between the light side and the dark side; they emphasized the importance of following the path of light. For some, the warnings were not enough and the temptation was too great: inevitably, some Jedi embraced the dark side and used their powers to bring great evil upon the galaxy.
Such tragic events endured in Jedi lore. One of these infamous incidents occurred four millennia prior to the rise of the Empire: the fall of the Jedi Exar Kun and Ulic Qel-Droma helped bring about the Great Sith War.
During the time of the Republic, ten thousand Jedi served the Republic and defended its vast territory. They identified potential recruits early in life, usually within the first six months of a child's existence. As infants, those attuned to the Force and accepted by the Jedi Council were taken to begin their training.
Older children, if identified later in life as being Force-sensitive, were refused training in most cases; the Jedi believed that the fear and anger in older children made them too susceptible to the dark side, and so it was unwise to train them.
All characters playing in this era that are Jedi Padawan learners have a master. While there may be times when the master and the Padawan travel together, most of their interaction happens between adventures, while all characters are training and improving. The master is often a gamemaster character, offering training, advice, and aid when the gamemaster feels such aid is appropriate and necessary.
Unfortunately, by the end of this time period, Anakin Skywalker has turned to the dark side and the Emperor has slaughtered nearly all the Jedi.
Then came the Dark Times: the Jedi purge has been completed. All but a handful of Force-users—let alone fully trained Jedi—were exterminated or corrupted to the dark side and placed in the service of the Emperor.
Force-sensitive individuals, such as Luke Skywalker and Leia Organa, were hidden from the Empire and cut off from their heritage. More powerful Force-users, such as Obi-Wan Kenobi and Yoda, purposely disappeared and worked to stay unnoticed.
Jedi characters in this era eventually attract a teacher, though the training these Force-users provide is haphazard at best. A would-be Jedi learns by experience, through occasional meetings with other Force-users, and even by studying with beings who follow other Force traditions. It's not easy, which is why Jedi in this period are few and far between, and few reach the level of power exhibited in earlier or later periods.
After the defeat of the Empire, during the time of the New Republic, Luke Skywalker has trained about one hundred Jedi and identified perhaps a dozen others in need of training.
Prominent Force-users such as Mara Jade Skywalker and Corran Horn help Skywalker train and coordinate the efforts of these Jedi, while promising students such as the Solo children and Ganner Rhysode show great promise for the future.
Jedi characters again receive a higher-level mentor who provides training and advice between adventures or when the gamemaster deems such interaction to be warranted and important to a mission.
One of the first things that a Jedi must learn is the Jedi Code; this philosophy lays the groundwork for the mastery of the use of the Force.
• There is no emotion; there is peace.
• There is no ignorance; there is knowledge.
• There is no passion; there is serenity.
• There is no death; there is the Force.
The Jedi must carefully observe the rules of the light side of the Force to maintain harmony with herself and the universe around her.
The light side is created and sustained by life. The Jedi acts to preserve life. To kill is wrong.
Sometimes it is necessary to kill. The Jedi may kill in self-defense or in defense of others, especially the weak and the good. The Jedi may kill if, by her action, she preserves the existence of life. However, the Jedi must never forget that killing is inherently wrong. Death is a stain upon the Jedi's spirit.
The Jedi seeks knowledge and enlightenment, peace and harmony. The Jedi wishes to defeat those who would wipe out such qualities—those who would inflict death, tyranny, or ignorance upon others—yet the Jedi should never act out of fear or hatred. A Jedi must act when calm and at peace with the Force. To act with anger filling one's spirit is to risk temptation to the dark side.
Jedi should seek nonviolent solutions to problems—but this isn't always possible. Sometimes, killing or fighting is the only answer available. Sometimes it is even the best answer. But that doesn't mean the Jedi shouldn't try to find an alternative.
A Jedi acts from wisdom, using persuasion and counsel over violence and Force powers. Force powers are to be used to serve the interests of the light.
Using the Force for personal aggrandizement, for personal power or wealth, or for convenience when other means would be more prudent—all of these traits are of the dark side.
A Jedi cannot allow evil to occur by inaction—a Jedi who voluntarily stands by and allows evil to be committed is encouraging the forces of darkness.
Jedi are also bound by the actions of those around them. It is not acceptable for a Jedi to associate with those who willfully choose to commit evil.
When a Jedi is confronted by a situation where evil is being committed, the Jedi must act to prevent that evil. There are a variety of means at the Jedi's disposal—persuasion, creating a distraction, armed action, or simple mind tricks—but intervention is necessary.
The Jedi lives in harmony with the Force, sensing its flow, drawing upon its energies… and sometimes perceiving "disturbances" and "presences" in that flow.
The actions of others can cause disturbances in the Force. A lone individual's impression might be like a candle flickering in the wind, while a great tragedy or act of great good may be like a sudden burst of lightning. Those who manipulate the Force often and with great power shine like the light of a sun.
Each time a Jedi draws upon the Force, there is a slight tremor as the Force is subtly altered. If the Force is used sparingly and with harmony in the natural order of things, such tremors are slight and barely detectable even at close ranges.
Those who frequently use the Force cause many, many tremors. When the Force is relied upon—used constantly to bend the universe to fit the will of the user—such tremors may be great enough that Jedi on distant planets may detect the user. Those who use the Force as a crude instrument of power are very likely to come to the attention of others.
New Jedi students are particularly likely to be detected. In their desire to master their powers, they often manipulate the Force… yet their dabblings, if too frequent, draw the attentions of other nearby Force-users. The purge of the Jedi was facilitated by servants of the Emperor who detected, tracked, and exterminated novice Jedi.
Some Jedi experience premonitions, dreams, and visions. Sometimes these events seem to be little more than random, impressionistic images, but at other times they are crystal clear glimpses of past, present, or possible future events.
There is much debate as to the cause of these phenomena—perhaps it's the Jedi's subconscious at work, or perhaps it's simply a different way of sensing tremors in the Force—but these occurrences have been known to warn Jedi of impending danger or to summon them to "crisis areas" where their unique abilities are needed.
Source: REUP: 148