Ark of Truth
Sophisticated Ancient technology capable of brainwashing anyone who gazes into the active unit into believing anything programmed in the device. The device, created by a scientific-focused Alteran named Amelius millions of years ago, was originally constructed with the intention of guiding Origin's religious followers from the their destructive, genocidal path.
Despite facing annihilation, the scientific Alterans believed use of the ark on their religious brethren would destroy their principles and end their corner of society. Instead, they left the device behind on Celestis and believed it destroyed during their exodus from the Ori galaxy.
The scientific Alterans would eventually discover the Milky Way Galaxy, leave their legacy as the Ancients, and ascend. The religious Alterans would eventually become the ascended Ori and use the Origin doctrine to persecute and destroy all who opposed them.
When the Ori made their religion known in the Milky Way, a long and bloody conflict eventually convinced Morgan Le Fay to prevail upon the ascended hierarchy and allow her to temporarily interfere with the lower planes of existence. They authorized her to guide Daniel Jackson and SG-1 to Celestis and the hidden ark, where it was taken to the city of Celestis and forcibly used against the Doci and Priors.
With these followers no longer transferring their energy of worship to the ascended beings, Adria -- the last remaining Ori -- was on equal grounds with Morgan Le Fay. Intent on preventing her from taking any more lives, Le Fay occupied Adria in ascended combat for all eternity.
KEY EPISODE
The Ark of Truth - Intent on stopping the bloodshed in the Milky Way, SG-1 embarks on a mission into the heart of the Ori galaxy to uncover the Ark of Truth and use it against the Ori followers.