After taking on Merlin's consciousness to build the Sangraal and destroy the Ori, Dr. Daniel Jackson began receiving visions of Merlin with a piece of Alteran technology called the Ark of Truth and a mountain erupting over it which he believed to have been left behind by Merlin when he inhabited Daniel's body. As the Ark of Truth could brainwash the followers of the Ori into believing that the Ori were not gods, the Tau'ri began to search for the device.
Earlier in the war, Dakara had been devastated when Adria targeted the Dakara superweapon with the weapon on an Ori warship. With Dakara having been the first place the Alterans landed when they arrived in the Milky Way galaxy, Daniel believed that the vision referred to the planet. Daniel led SG-1 in searching the ruins for days before finally uncovering a sealed chest that he believed to be the Ark of Truth. (SG1: "The Quest, Part 2", "The Shroud", "The Ark of Truth")
As Dr. Daniel Jackson and Vala Mal Doran argued over opening the chest, Teal'c noticed several Ori fighters approaching while Lt. Colonels Cameron Mitchell and Samantha Carter were engaged by Ori soldiers. The fighters bombed the area while Mitchell and Carter were unable to hold out against the onslaught of Ori soldiers, forcing them to fall back to the others' position.
However, the retreat left SG-1 trapped as the only way out of the ruins was blocked by the Ori soldiers. With no other choice, Daniel began attempting to open the chest in the hopes of using the Ark of Truth against the Ori soldiers. The Ori Commander, Vala's estranged husband Tomin, arrived and demanded their surrender and promised that their lives would be spared in exchange. Tomin warned that their position had been targeted from space by an Ori warship and if they didn't surrender, they would be destroyed. With Daniel unable to open the chest, Vala suggested having the Ori soldiers open the chest instead and Mitchell reluctantly agreed to surrender.
The Ori soldiers surrounded SG-1 who dropped their weapons. Tomin questioned what they were doing there, but when Mitchell returned the question, the Administrator entered the ruins and claimed that the Ori's power didn't need to be questioned. The Administrator demanded to know what the artifact was and Daniel told him that it held the secrets to destroying the armies of the Ori and that the Administrator didn't want to open it. As predicted, the Administrator ordered the chest opened anyway with Tomin resorting to blasting it open. However, the chest did not contain the Ark of Truth but rather some scrolls that crumbled to dust after being picked up to SG-1's surprise.
The Administrator ordered the deaths of SG-1, but Tomin argued with him about the order as he had given them his word that SG-1 wouldn't be harmed if they surrendered. The Prior threatened that Tomin would burn in the Fire of Everlasting Torment if he failed to comply and Tomin reluctantly turned his Ori staff weapon on SG-1. Vala told Tomin not to do it and that the Administrator couldn't hurt him and asked Tomin to trust her as they trusted him. Mitchell and Daniel told Tomin that while Tomin thought that the Prior was testing him, the Administrator was actually forcing Tomin to do it because for some reason beyond the Administrator's comprehension, he was completly powerless.
As the Administrator demanded that Tomin kill SG-1 more frantically, Tomin lowered his staff weapon. In desperation, the Administrator tossed aside his staff and grabbed Tomin's weapon to do it himself. However, Mitchell elbowed an Ori soldier in the face and shot the Administrator with the soldier's staff weapon, killing him.
Mitchell dropped his weapon and Tomin, shocked, ordered his soldiers not to fire. Carter revealed to Tomin the Prior disruptor that SG-1 had hidden nearby in the ruins which had been blocking the Prior's powers. Confronted with proof that the Ori were not gods, Tomin surrendered to SG-1. (SG1: "The Ark of Truth")
After surrendering, Tomin defected to the Tau'ri and joined SG-1 in returning to Earth where he provided the SGC with all of the intelligence he had on the movements of the Ori Army. Though SG-1 failed to find the Ark of Truth in the Dakara ruins, Tomin helped Dr. Daniel Jackson decipher his vision as instead pointing to Ortus Mallum in the Alteran Home Galaxy. (SG1: "The Ark of Truth")
- Though Tomin is stated to have surrendered and returned to Earth, its never revealed what happened to the other Ori soldiers under his command or the Ori ship in orbit and the fighters that were seen. It's possible that Tomin ordered his men to allow SG-1 to leave unharmed with his position and the shocking death of the Administrator causing them to comply without a further fight.