Though the same species as the Goa'uld, the Tok'ra are a resistance movement who live in voluntary symbiosis with their human hosts -- and thus refuse to be called "Goa'uld" because of their philosophical differences.
More than 2,000 years ago a Goa'uld queen, Egeria, realized what true evil the species was and made a decision to turn against the ways of Ra and the System Lords. All her offspring have genetically inherited the same ideals, and the Tok'ra (literally meaning "Against Ra") movement was born.
The Tok'ra become easily offended if their symbiotic creatures are referred to as Goa'uld, believing that they are vastly different then their Goa'uld brethren. They have been mercilessly hunted by the System Lords since their formation.
The Tok'ra are always on the run, changing the location of their base of operations every few years and operating multiple bases simultaneously. They live in subterranean tunnels they grow from special crystals. Once they arrive on a planet they immediately move underground with these crystals, forging corridors and rooms. This is how they have remained greatly undetected by the System Lords for thousands of years.
Often Tok'ra operatives are sent on missions to infiltrate and subvert the plans of the System Lords. Many Tok'ra spies have been implanted in various Goa'uld groups across the galaxy, rarely being discovered.
The Tok'ra are governed by the Tok'ra High Council. To keep from being entirely wiped out, there is more than one base of operations -- though one base is typically larger than the smaller cells, functioning essentially as a temporary Tok'ra homeworld. Since SG-1 met the group, they have moved to the desert planet Vorash, then to the forested world of Revanna. When the Goa'uld Zipacna (in the service of Anubis) discovered their location and attacked, the entire base was wiped out -- leaving only those Tok'ra in cell bases and away on missions as survivors.
Though the group has sustained many casualties over the years, their determination to wipe the Goa'uld scourge from the face of the galaxy is stronger than ever. Their long-term goal has been to keep the System Lords feuding with one another, so that no one Goa'uld can rise to dominant power. With the development of a symbiote toxin, however, they have begun to act more aggressively, hoping to one day exterminate the Goa'uld completely.
HOMEWORLD - Unknown
FIRST APPEARED - In the Line of Duty
In the Line of Duty - The S.G.C. learn of the existence of the Tok'ra when Jolinar of Malkshur hides within the body of Samantha Carter.
The Tok'ra, Part 1 - Carter's memories of Joliar lead the team to a meeting with the Tok'ra, who refuse an alliance with Earth.
Tok'ra, Part 2 - The Tok'ra agree to an alliance with Earth when Jacob Carter becomes host to the old and wise Selmak.
Serpent's Song - Martouf and the Tok'ra arrive on Earth to advise the S.G.C. after Apophis is captured.
Show and Tell - Jacob and the Tok'ra help the SGC fight off a squad of rebel Re'tu set on the destruction of all human life.
Into the Fire - A Tok'ra spy within Hathor's ranks helps SG-1 escape her clutches.
Seth - Jacob returns to Earth to help SG-1 find a Goa'uld who has been hiding on Earth for centuries.
Deadman Switch - SG-1 are forced to help a bounty hunter capture his prey -- Korra, whom they discover is a Tok'ra.
Jolinar's Memories - Martouf and SG-1 infiltrate Sokar's hellish prison moon in an attempt to rescue Jacob Carter.
The Devil You Know - Martouf, Jacob and SG-1 escape Netu, just as the Tok'ra Aldwin is sent by the council to destroy it.
Pretense - When Skaara wins control over his body, the Tok'ra are called to extract the Goa'uld Klorel from him.
Upgrades - The Tok'ra scientist Anise uses SG-1 in an experiment with alien devices that give them superhuman abilities.
Crossroads - SG-1 brings to the Tok'ra a Jaffa priestess who believes she has convinced her mature symbiote, Tanith, to join them. The Tok'ra allow it, knowing that Tanith is a spy for the Goa'uld, so that they can use him to channel disinformation.
Divide and Conquer - As the Tok'ra-Earth alliance is formalized, Martouf is killed when it is discovered that he has been programmed by the Goa'uld to kill the President.
Tangent - Carter and Jackson enlist help from Jacob to rescue their teammates, who are trapped in a ship headed into deep space.
The Serpent's Venom - SG-1 joins Jacob on a mission to sabotage an alliance between Apophis and Heru'ur.
Absolute Power - Aldwin visits the S.G.C. to question Shifu, the Harcesis child who possesses all the knowledge of the Goa'uld.
Exodus - SG-1 helps the Tok'ra evacuate Vorash before causing the sun to go nova, in a plan to destroy Apophis's fleet. Tanith is exposed as a spy, but escapes.
Enemies - Jacob and SG-1 must defeat Apophis and a swarm of Replicators and return to their own galaxy.
Summit - The Tok'ra enlist Dr. Jackson in a plot to infiltrate a meeting of seven System Lords and kill them -- the first step in a plan to exterminate the Goa'uld with a symbiote poison. But their base on Revanna is discovered and attacked by Anubis.
Last Stand - The Tok'ra suffer a major defeat at the hands of Anubis, who destroys the Revanna base -- though SG-1 escapes with the poison formula. Only Jacob and those Tok'ra away on missions survive.
Fail Safe - A Tok'ra operative arrives to rescue SG-1 after the team saves Earth from a meteor.
Meridian - When Daniel is exposed to a lethal dose of radiation, Jacob tries to save his life with a healing device -- but Daniel asks him to let him go.
Descent - Jacob and the team investigate a seemingly abandoned Goa'uld mothership that has arrived in Earth's orbit.
Frozen - The Tok'ra Torran arrives to offer O'Neill his only way to live -- a symbiote named Kanan.
Abyss - Torran stubbornly refuses to allow the SGC access to Kanan's mission reports to aide their efforts to rescue O'Neill, though Hammond eventually forces him to do so.
The Other Guys - SG-1 allows themselves to be captured in order to obtain information from Khonsu, a Tok'ra spy -- who is found out and killed.
Allegiance - When another Tok'ra base is attacked, refugees flee to Earth's alpha site, where they clash with the rebel Jaffa -- and find an invisible assassin.
Cure - The Tok'ra discover that their queen, Egeria, is alive -- but near death on a world where her offspring are used to create a potent drug.
Paradise Lost - A Tok'ra ship recovers O'Neill and Maybourne when they are stranded on an alien moon, and Jack requests that they find a nice planet on which Maybourne can settle down.
The Changeling - The Tok'ra announce that they have developed a version of tretonin specifically for Jaffa physiology, since SG-1 introduced them to the Pangarans.
Prophecy - The Tok'ra Sina visits the S.G.C. with important information about the System Lords, and Baal's vulnerable position.
Death Knell - Following accusations that their operative may have been responsible for leaking the location of the Alpha Site, the Tok'ra sever their alliance with Earth and the Jaffa Resistance -- for the time being.
Endgame - The Tok'ra operative Zarin falls victim to her people's own technological development, symbiote poison, when agents of the Trust attack her world.
Reckoning, Part 2 - Jacob/Selmak assist Earth and the Jaffa on Dakara, where they activate an Ancient weapon that eliminates all Replicators in the galaxy.
Stargate: Continuum - SG-1 attends the extraction ceremony for Baal, as the Tok'ra celebrate the end of the last of the System Lords in a sprawling city on their new homeworld.