A Tok'ra symbiote once blended with the Tok'ra host Saroosh, Selmak chose to blend with Jacob Carter to save both of their lives. Selmak was said to be good company with a wonderful sense of humor. He was among the oldest and wisest in the Tok'ra ranks, and maintained strict loyalty to their cause: the total destruction of the Goa'uld.
Selmak was an extremely positive influence on the crusty Air Force general, but had also been known to by irritated by Jacob. He influenced his host to return to Earth to resolve very personal issues between Jacob and his son, Mark.
Selmak successfully saved SG-1 on countless occasions, and with his knowledge continued to be an asset to the Tok'ra resistance and their plans to annihilate the Goa'uld forever.
He also played a vital role in the destruction of the Replicators, when he assisted in resetting the Dakara super-weapon. At that time he knew he was coming to the end of his life and had offered to leave Jacob before it was too late. Jacob, however, fearing that Selmak's knowledge was vital to the outcome, refused the offer.
Shortly afterwards Selmak became too weak to release his host, lapsed into a coma and died, taking Jacob with him.
The Tok'ra, Part 1 - Her host Saroosh dying of old age, Selmak must find a new host -- or die with her dear friend.
The Tok'ra, Part 2 - Jacob's life is saved when he agrees to become joined with the Tok'ra Selmak, making him Earth's official liaison to the Tok'ra -- the S.G.C.'s new ally in the fight against the Goa'uld.
Show and Tell - Selmak helps the S.G.C. determine whether or not Re'tu have infiltrated the base.
Seth - Jacob helps SG-1 track and kill the Goa'uld Seth, who has been hiding on Earth for thousands of years. Prompted by Selmak, Jacob patches things up with his estranged son, Mark.
Fragile Balance - Jacob/Selmak arrive to render his assistance to the S.G.C. when a teenage boy shows up claiming to be Jack O'Neill -- but who is dying of genetic degradation.
Evolution, Part 1 - Selmak shares his expertise in Goa'uld history, as well as uncovering the mystery behind the super-soliders.
Evolution, Part 2 - Jacob/Selmak use the Kull warrior's armor to penetrate the Stargate forcefield on Tartarus, disabling the planet's sensors to allow the rest of the team to infiltrate Anubis's secret base.
Death Knell - Selmak assists with the modification of a T.E.R. for use against the Kull Warriors, and also discovers that he is no longer trusted by all the Tok'ra.
Reckoning, Part 2 - Selmak assists Samantha Carter in the resetting of the Dakara weapon.
Threads - Jacob informs his daughter of Selmak's condition. Soon after both Selmak and Jacob die.