The name Tok'ra literally means "Against Ra." The Tok'ra are a small alliance of Goa'uld resistance whose stated goal was the destruction of the System Lords and a change in the ways of the Empire. The great Queen Egeria had been a Goa'uld, but she broke away from the Goa'uld empire over 2000 years ago and came to Earth to stop the Goa'uld from taking humans as slaves. She founded the Tok'ra movement through her offspring before she was captured by Ra, who imprisoned her in stasis on Pangar, although for thousands of years she was believed to be dead.

Both the Goa'uld and the Tok'ra are symbiotes, parasitical beings who pass on knowledge through genetic memory, and both can exhibit the characteristic glowing eyes and deep voice. However, the Tok'ra do not believe in taking hosts against their will. The Tok'ra symbiote blends with a host by choice, resulting in a truly symbiotic relationship in which the symbiote and host share a body, knowledge, and feelings. Unlike the Goa'uld, Tok'ra enter a host through the mouth rather than the back of the neck because many find the neck scar very unsettling, and a Tok'ra symbiote can leave a host at will. When a symbiote dies, it releases toxins which would kill the host, but a symbiote may prevent the host from dying by preventing the release of the toxins, a final selfless act which requires a certain amount of energy and a conscious effort. The Tok'ra have also almost perfected the process of safely removing an unwilling symbiote from its host by instantly killing the symbiote before the toxins are released. Symbiotes do not have a gender, but rather take on the gender of the host, and they are capable of curing most health problems in a human host, including cancer and arthritis. Physical trauma can also be healed by a symbiote, although it is much more difficult to repair than disease. The lifespan of a Tok'ra host is double that of a human, but rarely more than 200 years, and they do not use a sarcophagus to extend life further, believing that it takes away "kalach," or one's soul.

Since very few Goa'uld came over to the Tok'ra side, and none within the past few hundred years, Tok'ra numbers have diminished over the centuries because of a lack of new hosts, resulting in zero or negative population growth. The Tok'ra are infiltrators who use disguise and subterfuge to achieve their goals. They are hunted and despised by the Goa'uld and must continually flee to new planets to establish their bases. When they arrive on a planet, they go deep underground and use technology to plant crystals which grow tunnels, similar to a geode. When the Tok'ra move on, the vanishing tunnels collapse and destroy the network. Tok'ra operatives infiltrate the domains of the System Lords, and despite the need for their bases of operation to be scattered in secret across the galaxy, the Tok'ra are united by the governing body of the Tok'ra High Council.

SG-1 first learned of the Tok'ra when Jolinar of Malkshur took Carter as a host on Nasya. The memories of Jolinar left behind in Carter's mind led SG-1 to P34-353J, where they encountered Garshaw and Martouf and formed a tentative alliance. Since Jacob Carter agreed to become a host to the respected Tok'ra leader Selmak, the Tok'ra have become strong friends and allies of Earth, and although they have not readily shared all intelligence or information, the Tok'ra have willingly shared technology with Earth, such as the teltac, TER, memory recall device, zatarc detector, shield generator, and tretonin. The Earth-Tok'ra alliance was formalized in an official treaty which provided for the full exchange of all potential sources of information pertaining to the Goa'uld.

The opportunity to share vital intelligence was part of the reason that O'Neill reluctantly agreed to become a temporary host for Kanan, who could cure him of the virus that threatened his life. However, a true blending never occurred, and Kanan broke one of the highest laws of the Tok'ra, suppressing the host and taking control of O'Neill's body until he was captured by the forces of Ba'al and fled the host. O'Neill has remained cautious in his relations with the Tok'ra, but Tok'ra operatives such as Anise, Ren'al, and Sina have cooperated as liaisons to Earth, and Jacob, Martouf, and Aldwin have collaborated with the SGC on many missions, including battles with the Reetou, Replicators, Seth, Sokar, Tanith, Heru'ur, Apophis, Anubis and his Kull Warriors, and the System Lords.

After thousands of years of infiltration, the Tok'ra were in a position to eliminate key System Lords at the summit of Hassara which would clear the way for a final decisive move against the entire Goa'uld population by using a poison that targets symbiotes. However, the rise of Anubis thwarted their plan, and the Tok'ra were dealt a crushing blow when their bases at Revanna and the Risa System were wiped out by forces loyal to Anubis. Since then, only a fraction of their number remains. The discovery of Egeria on Pangar was too late to save her life and to rejuvenate the Tok'ra movement, and the Tok'ra now face extinction.

Severely weakened and on the run, many Tok'ra were evacuated to the Alpha Site until a new base could be established, and there they began to regroup and to overcome their historical distrust and hatred of the Jaffa in order to begin cooperating with the Rebel Jaffa movement. Their cooperation was short lived, however. Following the destruction of the Alpha Site by Anubis's Kull Warriors, the alliance among the Tok'ra, Rebel Jaffa, and Tauri began to crumble. The Tok'ra claimed that since their alliance with the Tauri, Earth's tendency to provoke direct confrontation with the Goa'uld had resulted in the deaths of more Tok'ra than in the previous hundred years combined, and that for a race on the brink of extinction, a continued alliance was something which they could no longer afford. Furthermore, the Tok'ra High Council, of which Selmak was a member, had begun to question Selmak's loyalties and the influence of Jacob Carter's sympathies toward the humans of Earth. As the Tok'ra High Council withdrew from the alliance, Jacob found his support within the High Council diminishing, but he chose to remain with the Tok'ra in an attempt to rebuild the alliance.

For nearly a year, Earth had very limited contact with the Tok'ra, but when the Replicators entered the galaxy and launched a war against the Goa'uld, Jacob, whose relationship with the High Council remained strained, returned to the SGC hoping to find a way to stop the Replicator threat. He shared a Tok'ra receiver with the SGC which allowed Goa'uld ships to be monitored, and he cooperated with Carter to modify the Ancient device on Dakara with which the Replicators were finally defeated. Following the battle, Selmak, weakened by age, slipped into a coma, and Jacob was destined to die with him. Despite the strained relationship between Earth and the Tok'ra, both remained allies, and several Tok'ra visited Earth to pay their final respects to an honored leader as Selmak and Jacob quietly passed away.

Since the fall of the System Lords, the goal of the Tok'ra has been realized, and Earth and the Tok'ra have remained allies, sharing intelligence and resources in the battle against the Ori. Tok'ra ships were among the allied armada that faced the Ori invasion at the supergate. In their joint effort to rid the galaxy of the Ori, the Tok'ra agreed to cooperate with SG-1 after Ba'al had taken Adria as a host. News that the leader of the Ori army had been captured came as a ray of hope to the Tok'ra, and Ta'seem arrived to perform the delicate surgery that attempted, unsuccessfully, to replace Ba'al's symbiote with the symbiote of Zanuf, a more cooperative Tok'ra.

Cross Reference: Aldwin, Alpha Site, Anise, Ashrak, Jacob Carter, Samantha Carter, Cordesh, Delek, Egeria, Freya, Garshaw, Goa'uld, Goa'uld Language, Hassara System, Hebron, Holographic Projection, Jalen, Jolinar, Kanan, Kelmaa, Khonsu, Korra, Lantash, Malek, Martouf, Memory Recall Device, Ocker, Jack O'Neill, P34-353J, P3X-984, Pangar, Pangarans, Per'sus, Raully, Rebel Jaffa, Ren'al, Replicators, Revanna, Rosha, Selmak, Shan'auc, Sina, Stasis, Symbiote Poison, System Lords, Tanith, Ta'seem, Thoran, Tok'ra Communicator, Tok'ra Receiver, Tok'ra Tunnels, Tretonin, Vorash, Yosuuf, Zarin, Zatarc Detector

Episode Reference: In the Line of Duty, The Tok'ra, Serpent's Song, Show and Tell, Seth, Deadman Switch, Jolinar's Memories, The Devil You Know, Pretense, Upgrades, Crossroads, Divide and Conquer, Tangent, The Serpent's Venom, Absolute Power, Exodus, Enemies, Summit, Last Stand, Fail Safe, Meridian, Frozen, Abyss, Allegiance, Cure, Paradise Lost, The Changeling, Prophecy, Fallen, Fragile Balance, Evolution, Death Knell, Endgame, Reckoning, Threads, Dominion