About sixty years before contact was reestablished with Abydos, there were two Tau'ri children who found an Ancient artifact that let them dial out to a boreal planet that served as a multi-gate hub. They visited a planet that proved to be depopulated, where they discovered one of the unascended Ori in cryosuspension who then escaped with them in tow. While they were fleeing the planet that had been devastated by Ori technology, the gate's power source was depleted. The proto-Ori tried to capture the Tau'ri homeworld but was stopped by an ascended being who trapped her on a third world. Unable to dial out, she remained there and began to use her superior technology to dominate the indigenes. The ascended being seeded the new world with two Tau'ri and then shut down the gate on his side. Due to relativistic time dilation, subjective time on the Tau'ri homeworld passed much slower.
After two generations on their world, the Tau'ri discovered some unstable gate technology that let them return to the world where, over a millenium of subjective time, the proto-Ori had gained a foothold. She had enslaved some of the indigenes by virtue of her superior knowledge and abilities, driven other species underground, and even removed the Tau'ri from power in most of her sphere of influence. Of the four gate team members who reestablished contact, she captured one and convinced him to collaborate. The indigenes believed that she had considered recruiting him as a doci, but he proved recalcitrant. She resolved instead to use him to lure the other Tau'ri out of hiding, but they made contact with the ascended being before this plan succeeded. The Tau'ri was extracted by special operations conducted by the indigenes, at which point the proto-Ori invoked the founding charter of the system. The ascended being took the place of the Tau'ri turncoat and was killed in his embodied form, but reascended and returned to destroy the army that the proto-Ori had amassed. After remaining on the ascended being's world for several years, they were gated back to their homeworld in their original state, with their memories intact. This is believed to contravene the Ancients' laws on intervention, which is why the original Tau'ri who witnessed the founding of the ascended being's world did not believe him to be an Ancient.
Ninth Day of Christmas, following my personal LJ tradition (started in 2003):
"The Lion of Judah"
Words: Fanny Crosby (1820-1915)
Music: W. Howard Doane (1832-1915)