Ark of Truth
Sophisticated technology capable of brainwashing anyone who gazes into the active unit into believing anything programmed in the device. The device was created by a scientific-focused Alteran named Amelius millions of years ago (before his people migrated to the Milky Way Galaxy and eventually became the Ancients). The Ark was originally constructed with the intention of guiding the fanatical followers of Origin from the their destructive, genocidal path.
Despite facing annihilation, the scientifically-minded Alterans believed use of the ark on their brothers to forcibly alter their views would destroy their own principles. Instead, they opted to leave the device behind on Celestis, and believed it to have been destroyed during their exodus from the Ori home galaxy.
The Ark measures roughly 2 x 1 x 1 meters, and has a complex locking mechanism on top of the device. Once it is open a bright and powerful energy emanates out of the top, altering the views of those within immediate proximity. The energy is also capable of being translated through the Ori Priors' interconnected staff devices, allowing the effects of the Ark to be quickly translated to all Priors throughout multiple galaxies.
Having eliminated the ascended Ori almost entirely (with Adria being the sole exception), SG-1 traveled to Celestis to locate the Ark buried in a cave. They managed to activate the device, convincing the Ori's mortal followers to end their military invasion of the Milky Way.
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.