“Talion” is episode seventeen of season ten of Stargate SG-1.
This opens with SG-1, except Teal’c, combing through the wreckage of a destroyed camp. Both Teal’c and Bra’tac are discovered in the wreckage, and they’re both badly injured.
Teal’c and Bra’tac had been attending a Jaffa conference that was planning what to do about the Ori, when several explosions destroyed the place, killing many of the Jaffa.
Teal’c gets information that this had been carried out by Arkad, a previously unheard of (in the series at any rate) Jaffa who has amassed great power and plans to bring the Jaffa to the Ori. Teal’c has a grudge against Arkad, and goes after him – without the backing of the SGC.
Arkad, meanwhile, contacts the SGC himself and says that he isn’t behind the attack, but that he knows who is. Consequently, the IOA order Teal’c stopped, so SG-1 are sent after him.