Jedi Order
In the dawn of interstellar travel, it is told that the best and brightest philosophers, poets, priests, warriors, monks and mystics began to compare their observations on the assorted "supernatural" powers they had discovered over the ages. At some point it is agreed that they gathered to formalize their growing discoveries into a mysterious form of energy that they called the Force. The culmination of these efforts led to the establishment of the Jedi Order. As the Core Worlds? grew in importance and population, it was only natural the new Order would locate itself at the fastest growing of these to take advantage of the dynamism of the new cultures. These core world polities evolved quickly into what we could recognize today as the Galactic Republic, and thus began the long relationship between the two entities.
While not verifiably the oldest Force using tradition, it is certainly the premier organization dedicated to the study and advancement of the Force. Libraries were built recording the advancing knowledge, and the Order dedicated itself to peace, justice, and democracy as it saw these as the foundations for a stable, prosperous society in which it could thrive. When tyrranies threatened the democracies of the time, the Order opposed them. Though less organized and formal than today's Order, even at the time it was a formidable force, with members involved in many elements of society.
However, the accumulation of power cannot be done forever without misuse. Some Jedi succumbed to the Dark Side. For the most part, these were rare occurences in the early years, and such dissenters were brought back into the fold or destroyed. When a large group grew enough to challenge the leadership, a power struggle ensued that resulted in the exile of the Dark Jedi and these eventually developed into the Sith.
The Jedi Order has been regarded as the guarantors of peace, stability, and justice in the galaxy for thousands of years and when the elected government crumbled under the onslaught of Bellisarius, the Order was asked to step in by the Senate?. The transition was peaceful and accepted by the majority of the population over the muted opposition. For a period the Jedi Order was the government of the Galactic Republic and, while exceeding the expectations of most of the citizens in their remaining territories, even this disintigrated as an effective government in the face of the Dark Swarm. The Order is now mostly based in deep space, utilizing the knowledge gained from the Exordium project to stay one step ahead of the Swarm, in a tenuous truce with the Tion Principality and the Sith Empire in an effort to contain the Swarm. In effect, they are one of at least three, possibly more, hyper-advanced factions vying for power in a post-apocalyptic galaxy.