10 Plots From Stargate That Were Just Dropped

The season 4 episode of SG-1 'Divide and Conquer' saw an important summit between the Tok'ra and the President of the United States. When High Councillor Persis is meeting with some of SG-1 to go over the details, one of other US soldiers present attempts to murder him, seemingly against his own will. He is quickly killed and the Tok'ra Anise (who'd become a fixture over the past three episodes) deduces that he had become a Za'tarc.

Za'tarcs are, according to Anise, a form of mind-controlled agent who has a target to kill. They're like a sleeper agent, completely unaware that they've been compromised until their target presents itself and they have to kill them and/or themselves. Apparently this mind control only takes seconds as both O'Neill and Carter are under suspicion because they were alone in a corridor on a Goa'uld ship for about three minutes in the previous episode.

Despite being a hugely powerful tool at the disposal of the Goa'uld and proven to exist by the events that led to Martouf's death, they are never used again and only briefly mentioned once afterwards. The truth-telling device that was used to flush them out does make a reappearance, but not in connection with the Za'tarcs themselves.

Ironically, the Tok'ra High Councillor Persis would never be mentioned again and Tok'ra leadership organisation and their titles seemed to change whenever it was brought up...