Great War of Light and Darkness

The Great War of Light and Darkness was, at the time, the most devastating conflict ever fought in the galaxy. This war blurred the image of and the  being enemies. During this 28 year long war, the Galactic Republic and the and the Hutt Cartels surprisilingly allied themselves with the original Sith Empire and the Republic and its allies allied themself with the Jedi Civil War era Sith Empire which arrived in 5,000 BBY due to Darth Kryat manipulating time. Also the Republic forces and Jedi under Revans command alos arrived in 5,000 BBY due to Darth Kryat actions and quickly allied themselves with the Republic. Also remants of the Mandalorians that survived the Mandalorian Wars also traveled back in time and fought for the Republic. This grand alliance fought against the Sith Empire from the beginning of the. And the final faction of this war was the Mandlorian warrior race of 5,000 BBY and they later became the True Mandalorians.

Darth Kryat Experiments
Sometime between 30 ABY and 128 ABY Darth Kryat was exprementing with ancient Sith knowledge that concerned manipulating time. He was trying to change the timeline to make his ascension to power smoother and sooner by changing time to suit his goals. But instead he caused a tear in the time continum which resulted in the creation of countless differnt timelines and altenate realties. One of the realties that were created by Darth Kryat was a galaxy where multiple organizations of both the light side and dark side from various time periods and eras from the future suddenly appeared in 5,000 BBY and forever changed the fate of the galaxy forever.

The Arrival
In a event that would later be famoulsy called The Arrival which was a event that resulted in the arrival or sudden apperance of several organizations. The organizations that arrived in 5,000 BBY were the Jedi and Republic forces under Revans command. Also the surviving remnants of the Mandalorians at the end of the Mandalorian Wars also appeared in 5,000 BBY. The entire Sith Empire near the end of the Jedi Civil War appeared in 5,000 BBY too. And finally the Sith Empire at the start of the Great Galactic War as well appeared in 5,000 BBY. The sudden appearances of all these factions quickly led to war and unexpected alliances.