I made a brief history of what happened in the pre-republic era.

Pre-republic
Galaxy formed about 13 Billion BBY

Planets and people start evolving

1 million BBY The celestials are said to have formed the Corelian system
a. Celestials-The Celestials, also known as the Architects, were an ancient civilization who were present long before the dawn of the Galactic community.
b. Jedi and sith alike have speculated that the light and dark sides of the force was actually under the guidance of the celestials
c. They were considered one of the earliest and most potent cultures of their time that were identified by the colossal objects they had left behind. Like center point station .Their identities were considered largely a mystery due to lack of information on them. Evidence of their works led many to determine that the region of space was once visited by these stunningly powerful alien architects.[3] They were noted for being an advanced race that ruled the galaxy with these beings holding technology that allowed them to construct or even realign solar systems.[4] A number of species were known to have coexisted with this ancient race as far back as 100,000 BBY. These included and a bunch of other aliens
e. No one knows where they came from or what eventually happened to them
f. The brother sister and father also known as the ones who Anikan meet are said to be celestials


At 36,453 BBY Pholosphers and scientis from several star systmes gather on Tython to share mystical knowledge, and the force is discovered

At 35,000 BBY the infinite empire of the Rakata which uses the dark side of the force is officially established, The Infinite Empire, the first known major galactic government, was founded and ruled by the Rakata, a scientifically advanced speciesthat used their knowledge to conquer and enslave other species throughout the known galaxy, from Humans to Sand People.


At 30,000 BBY The infinite empire reach their peak of power, they build the star forge which is a really powerful factory for war materials which utilizes the power of a nearby star. At this same time on Korriban a sith king came into power. The sith were originally a species that lived on Korriban, and the sith king adas, was thought to be a chosen one because the pigments in his skin gave him a charcoal color rather than the normal red color. He was raised as a chosen one and continued to unite the sith nations under his rule, and stays in power for the next 300 years. He was large, smart, and skilled in sith magic
Traditionally, Sith magic, also known as Sith sorcery, was an arcane expression of Force ability first developed and practiced by the original Sith species through which they manipulated the power of the dark side. The very name of the Sith was adopted by the Dark Jedi Exiles of the Hundred-Year Darkness, who combined Sith mysticism with their own experiments into dark side power to create even more strange rituals and alchemical sciences. Sith magic, while as much a part of the dark side as endowments like Force lightning, was accessible only to those Force-sensitives who possessed an intrinsic relationship with the dark side. Through the recitation of spells, execution of hand gestures, and or the handling of various artifacts, darksiders were able to channel the raw power of the Force's malignant side to warp minds, alter the environment, andobliterate whatever obstacles stood in their way. Males who achieved mastery were known as Sith sorcerers, mages, magicians, or wizards, while females who practiced Sith sorcery were referred to as Sith sorceresses or witches.


27,700 BBY The Rakata arrive on Korriban at first they’re friendly and they teach Adas to use holocrons. Soon the Sith and the Rakata start fighting, and the sith win but Adas is killed in the process

25,783 BBY Several Tythan scholars begin to use their knowledge of the force to pursue power This leads to the Force wars, between the followers of Ashla (Light side) and Bogan (Dark side) The conflict took ten years, and is considered to be the first battle between followers of the dark and light side. Both sides utilized metal swords augmented through the force. The Bogan followers were defeated, and the followers of Ashla establish the Jedi, and they eventually left the world of Tythan which was considered to be the homeworld of the jedi.

25,200 BBY
A Major plague sweeps through the galaxy that kills only Rakata. As a result of this, twinned with subject species rebellions, the Infinite Empire collapses
During this period the Hutts continue to grown in power and expand their territory.

The pre republic period ends around 25,00 BBY