Author's note: This is the backstory for a story that's been in my head for a few months. Hope you all like it.
Disclaimer: I don't own the Harry Potter or Star Wars franchises, they are owned by J.K. Rowling and George Lucas respectively.
Chosen by Two Galaxies
Prelude
Twenty five thousand years before the formation of the Empire, natives of the planet Tython began to discover that they could access a mystical power. The Tythonians split into two camps, one that served the light, and one who served the dark. The two groups fought in a vicious war that lasted for many years. Over the course of many battles, a small third group began to emerge. This group served neither light or dark, and used the power through objects imbued with the power's essence and incantations, to change the physical world around them. This third sect retreated to a distant island, where they furthered their abilities, and waited out the war.
The war ended with the defeat of the followers of the darkness, but the planet was damaged immensely by the immense energies released by the combatants. Soon after the war ended, the Tythonians who followed the light, driven by the destabilizing planet, developed rudimentary space flight technology, and left the planet, forgetting their hermitic brethren in the process. The followers of the light developed their understanding of the energy that they now called the Force, and eventually encountered the newly formed Galactic Republic. Taking on the name Jedi, the tythonians spread their teachings across the galaxy.
Meanwhile, back on Tython, the hermits led a simplistic existence on their island. They used their power to create wards around the island to protect it from the energies devastating the planet. They managed to survive for almost twenty thousand years, passing on their teachings to their descendants. Finally, however, the wards began to fail. The Tythonians were unable to escape their planet through technology, as their isolation had left them technologically inept. Stretching their powers to the limit, they used the Force to create a rip in the fabric of reality, a portal to another galaxy. The Tythonians stepped through the portal, and arrived on a new world. Earth.
The Tythonians spread out among Earth's natives, and over time, they interbred with them, creating a small section of the population that could access and use the Tythonian's power. These people would eventually be called wizards. The tythonians taught the wizards how to harness their newfound power, but kept from them the darkest secrets of their power, such as the ritual that would create the portal back to their home galaxy. They didn't want this knowledge to be lost, so they created a secret group, consisting of only a few wizards at a time, who were entrusted with this secret, with the proviso that it would only be used in very extreme cases. The group continued on for thousands of years, protecting the last secret of the Tythonians, and never using it.
And so, eventually, the Tythonians died out, their legacy continued in the blood of the wizards. Eventually, the magical population grew to the point where their collective power created a Force nexus that permeated the entire planet. This nexus allowed others who were never a part of the wizarding community to be exposed to the power, creating the first muggle-borns. Unfortunatly, it had negative effects as well, as the nexus allowed the wizards to begin to feel both sides of the Force on a subconscious level. This created a schism in the wizarding community, as some succumbed to the lure of the darkness, while some others came into the light.
And this is where the world stands on October 31st, 1981.