- "Great holy armies shall be gathered and trained to fight all who embrace evil. In the name of the Gods, ships shall be built to carry the warriors out among the stars and we will spread Origin to all the unbelievers. The power of the Ori will be felt far and wide and the wicked shall be vanquished."
The Great Enlightenment was the name given by the Ori to their inter-galactic crusade against the races of the Milky Way to convert the galaxy to Origin, however the Ori were met with heavy resistance by the Tau'ri, Free Jaffa Nation, Asgard, Tok'ra, Serrakin as well as the Goa'uld and human-led Lucian Alliance.
Vala Mal Doran, Dr. Daniel Jackson, Lt. Colonel Cameron Mitchell and Teal'c found the Avalon cavern below Glastonbury Tor and among the treasures, an Ancient Long-range communication device. Using the terminal, Vala and Daniel connected to two people in the Alteran Home Galaxy, but during their use of the terminal, exposed the existence of the people in the Milky Way to the Ori. Before they could be killed, the terminal they were hooked up to was destroyed which brought them back to their own bodies. The Doci declared a holy crusade on the people of the Milky Way and promised that ships would be built to carry an army into the Milky Way. The Ori planned to gain as many followers as possible so they could become strong enough to eventually face the Ancients in battle and destroy them. The Ancients refused to interfere believing in free will enough that they will only interfere if the Ori take direct action.
In the meantime, while the army was being organized, the Doci sent Priors through the Stargate to convert Milky Way planets and gain more followers. If the planet refused conversion, they were wiped out, its population killed. The main tactic used was to fulfill "miracles" like healing the ill and making crops ready to harvest immediately and spreading the Prior Plague and cure people after they convert to make the Ori appear like Gods. If the people refused to convert, the plague was allowed to run its course and wipe out the population. In an encounter with a Prior who spread the plague on a primitive village, Stargate Command failed to find a cure and the people were only saved because they converted to Origin as their religion.
As part of their plan to bring a fleet to the Milky Way, a Prior attempted to build a Supergate to bring the ships as the Alteran Home Galaxy was very far away from the Milky Way and it would take a long time to get there otherwise. The first attempt took place at the planet of Kallana where they used the Goa'uld Nerus to trick the Tau'ri into helping power their planet collapsing force-field with their weapons. The plan nearly succeeded but is foiled by Vala who destroys the Supergate, but when she tried to ring back to the Prometheus, she was instead sucked into a black hole and sent to the Ori galaxy where she ended up in the rings of the village of Ver Isca and was found by a man named Tomin.
The Priors later made an attempt at converting or destroying Earth through the Prior Plague. However, an Ancient named Orlin descended to help find a cure to the plague. He helped finish a device that neutralized a Prior's powers and it is used to capture a Prior and get a blood sample in an attempt to find a cure. The attempt failed, but the Tau'ri learn from the Prior that the Ori were doing all of this to destroy the Ancients before Mitchell was forced to kill him. The attempt on Earth was foiled by the Jaffa, Gerak who was turned into a Prior. He cured everyone in the SGC and using antibodies isolated from that, a cure is found, however, the act cost Gerak his life and Orlin lost his memories and was placed in a mental hospital. The SGC spread the cure to planets that need it, and even an alternate reality that desperately needed a cure, and that method of attack was rendered useless.
In converting the planet of Tegalus, the Priors used a different method: they give the Rand Protectorate a weapons satellite to use against their enemies as Rand wanted weapons technology to fight their enemy the Caledonian Federation. The weapon proved powerful enough to destroy the battlecruiser, the Prometheus, although most of the crew managed to escape to Caledonia via Asgard teleporters. The Caledonians were ultimately given the Stargate so they could escape if they wish, but a war erupted after the talks broke down and both sides destroyed each other.
With their disease rendered useless, the Priors resorted to using the bug R-75 on planets that were reluctant to convert. They were used on at least a few planets, but didn't seem to be used often as they were only seen and mentioned once, so the Priors may have abandoned this method.
After the Sodan changed their minds and turn their backs on Origin, a Prior turned the Sodan warrior Volnek into a kind of zombie that can only be killed through complete destruction of his body and unleashes him on the Sodan. Only Lord Haikon survived the vicious massacre and Volnek was later killed by Mitchell and Teal'c. At the same time, Daniel discovered the existence of a weapon that could destroy Ascended beings, created by the Ancient Merlin in order to destroy the Ori.
Using a second Ancient Long-range communication device, Vala contacted the SGC through Daniel to warn them of the Ori fleet. She had been impregnated by the Ori in order to create a human representative for them and had also secretly joined the Anti-Ori underground in order to do her part in resisting the Ori. After a plan by the leader Seevis to destroy the Ori warships fails, Vala contacted Earth to warn them of the impending threat knowing that as the ships were leaving soon, there was another Ori Supergate in existence somewhere in the Milky Way. Vala was interrupted by her husband Tomin who killed Seevis and Denya, but was convinced by Vala that she was innocent and to take her with him when he went to war in the Milky Way. With this new information, the Tau'ri, the Tok'ra and the Free Jaffa began a search for the new Supergate while SG-1 continued searching for Merlin's weapon. 
Cha'ra of the Free Jaffa Nation managed to locate the Supergate and a fleet of ships made up of Tok'ra and Free Jaffa Ha'taks and Al'kesh, an Asgard mothership, the Odyssey and the Korolev formed a small group as they tried to destroy the Supergate, or failing that, stop any fleet that arrived. On the planet Camelot, SG-1 searched unsuccessfully for the anti-Ori weapon. They located the treasure hidden there, but learnt that the weapon which was called the Sangraal, was gone and find out the name of three planets where it could be located. Lt. Colonel Samantha Carter stayed on the Odyssey in the hope of coming up with a way to disable the Supergate, while Teal'c departed to enlist the help of the Lucian Alliance while Mitchell and Jackson arrived on the Korolev. At the Supergate, Carter attempted to dial out with Kvasir's help, but failed as the Ori dialed in and sent a fleet of four ships to the Milky Way with the effect leaving Carter stranded in space.
The crusade began at the Battle of P3Y-229. At the activation of the Supergate, the Ori Army sent four Ori warships through it as a first wave. It battled a O'Neill-class warship, the Odyssey, the Korolev and a fleet of Ha'taks from the Tok'ra, Free Jaffa Nation and the Lucian Alliance. However, their efforts were unsuccessful, as the Ori shields were too powerful for their weapons to pierce with the Ori's energy beams dealing incredible damage to the allied forces. During the battle, all but the Odyssey and the Lucian Alliance flagship were destroyed, albeit heavily damaged, although the fate of Kvasir's O'Neill is unknown. When the battle ended, Vala Mal Doran, on one of the ships, gave birth to her daughter Adria, and learned that she was Orici, an Ori in human form intended to let the Ori lead the Ori army without enticing the Ancients.
After leaving the system, the Ori fleet traveled to Chulak, since this world was the first to denounce the Goa'uld. One ship landed planet side to launch a ground invasion, while the other three remained in orbit. Bra'tac brought three Ha'taks to try and defend the planet, but they were destroyed. SG-1 and Bra'tac were rescued by the Odyssey, which had followed them once its hyperdrive was repaired, and Vala and Dr. Daniel Jackson (who escaped the Korolev's destruction by ringing to an Ori warship) were also beamed aboard, saving them from a Prior which attempted to kill them. Over the next week, the Ori conquered six more worlds, including two Jaffa strongholds.
In a plan to seal the Supergate, SG-1 traveled to Atlantis to cause a jump with a black hole, as well as locate the Sangraal, a weapon Merlin built to kill the Ori. While there, Dr. Daniel Jackson met the Ascended Ancient Morgan Le Fay, who told him of Merlin's intentions, and that she had taken the Sangraal and hid it on one of three worlds: Castiana, Sahal, and Vagonbrei. However, the Others prevented Morgan from telling him anything further. The plan to cause the jump eventually worked, and also resulted in the destruction of both an Ori warship and a Wraith Hive ship. 
Suffering massive losses, the Free Jaffa Nation, under Se'tak, used the Dakara superweapon to destroy the crew of an Ori warship. Adria retaliated by destroying the weapon and devastating Dakara, fracturing the Free Jaffa Nation, thus removing the only organized military force that could effectively combat them. The only survivors were SG-1 who were beamed out by the Odyssey at the last minute and Major General Henry Landry and Bra'tac who escaped through Dakara's Stargate at the last second.
Eventually, SG-1 and the System Lord Ba'al discovered the location of where Morgan hid the Sangraal. After discovering Adria in their midst, they were transported to a planet where they learned that Morgan had destroyed the Sangraal, but hidden the real prize: Merlin, held in a stasis pod so that he could one day rebuild the weapon. Merlin agreed to help them, but his body had aged too much while in the pod, and he transferred his memories to Daniel. Daniel built two phases of the device, but Adria found where they were and captured Daniel and the weapon. Adria believed that she converted Daniel to Origin and made him a Prior, but Merlin's consciousness was able to protect him. He made contact with SG-1, and convinced them and Major General Jack O'Neill to shut down the Supergate so that he could send the weapon through. They succeeded, but the Ori army regained control of the Supergate, sending another six ships into the galaxy. It is later revealed that the Sangraal did its job and destroyed the Ori.
SG-1 set a trap for Adria, but it was ruined when Ba'al kidnapped her and took her as a host. With the help of the Tok'ra, they removed Ba'al, but he released the symbiote toxin into Adria. Dying, Adria ascended.
When the Asgard realized that they were unable to repair the defects caused by their constant use of cloning, they decided to commit mass suicide and leave their technology and knowledge to the Tau'ri. Before this plan could be carried out however, three Ori warships launched an attack on Orilla, the Asgard homeworld. This forced the Asgard to speed up their plan and gave the Tau'ri their technology, including the new Asgard plasma beam weapons, which are capable of piercing the shields of the Ori warships. With this new technology, the Tau'ri are now a potential threat to the Ori fleet. 
End of the crusade
The crusade finally ended with the Ark of Truth, with a win for the humans of this galaxy. Morgan Le Fay began directing Dr. Daniel Jackson through dreams to search for the Ark of Truth, an Ancient device that will force the followers of the Ori to believe the truth about them. SG-1 searches the ruins of Dakara for it and apparently find it when they are captured by Tomin and his forces. SG-1 convince Tomin of the truth by killing the Prior that was accompanying him after they secretly used the Prior disruptor to negate the Prior's powers. Tomin was subsequently able to help them figure out that the Ark was likely in the Alteran Home Galaxy, although the team also learned that the Ori were intending to come after Earth. In an attempt to stop this, the team and Tomin takes the Odyssey to the Ori galaxy through the Supergate to find it and stop the Ori forces.
There they found out that the Ori are indeed dead but Adria has taken all of their power and is planning to conquer the universe and destroy the Ancients. The International Oversight Advisory tries to implement a plan to use the Replicators to destroy the Ori forces but things go bad until Lt. Colonel Samantha Carter manages to trigger a self-destruct in the Replicator forces. The crusade finally ends when Daniel, Teal'c and Vala Mal Doran activate the Ark forcing the Ori followers in the Ori galaxy to realize the truth severely diminishing Adria's power. Morgan Le Fay engages her in battle and the two apparently destroy each other. SG-1 takes the Ark back to the Milky Way where they use it to convince the Priors of the truth there as well ending the crusade.
With the end of the crusade, the Milky Way Galaxy was at peace once again. SG-1 started heading out on normal reconnaissance missions and the Ori Army returned home under the command of Tomin, their new leader. At some later point, Ba'al was finally tracked down and killed, and with his death and the end of this crusade all known threats in the Milky Way with the exception of the Lucian Alliance were gone which meant that the citizens of the entire Milky Way Galaxy were finally free to led their lives without any influence from any beings posing as Gods.
- Battle of Kallana
- Battle of Tegalus
- Battle of P3Y-229
- Battle of Chulak
- Attack on a Ori occupied world
- Fall of Dakara
- Battle of the Black Hole
- Quest for the Sangraal
- Fall of the Ori
- Capture of Adria
- Battle of the Asgard Legacy
- Battle of the Dakara Ruins
- Battle in the Alteran Home Galaxy
- Tau'ri-Ori skirmishes
Notes and references
- (SG1: "Threads")
- (SG1: "Ex Deus Machina")
- (SG1: "Ethon")
- (SGA: "Progeny")
- (SG1: "Off the Grid")
- (SGA: "The Siege, Part 3")
- (SGA: "Allies")
- (SGA: "Lifeline")
- (SG1: "Origin")
- (SG1: "Avalon, Part 2")
- (SG1: "Unending")
- Stargate: The Ark of Truth
- (SG1: "Counterstrike")
- (SG1: "The Shroud")
- (SG1: "The Pegasus Project")
- (SG1: "Camelot")
- (SG1: "The Quest, Part 1")
- (SG1: "The Fourth Horseman, Part 1")
- (SG1: "Talion")
- (SG1: "Beachhead")
- (SG1: "Flesh and Blood")
- (SG1: "Dominion")
- (SG1: "The Quest, Part 2")
- (SG1: "The Fourth Horseman, Part 2")
- Adria - Leader of the Great Enlightenment on Stargate Trading Card Game
- (SG1: "The Powers That Be")
- (SG1: "Crusade")
- (SG1: "The Scourge")
- (SG1: "Arthur's Mantle")
- (SG1: "Morpheus")
- Stargate: Continuum
- (SGU: "Air, Part 1")