Cure (S06E10)

SG-1 pays a visit to Panger, where a working Stargate has recently been discovered among some ruins. The Pangerans, who are a few decades behind Earth technologically, have developed a miracle drug called tretonin that makes the immune system "impervious to all disease." The Pangeran leaders, Tegar and Dollen, offer to share the secret of tretonin. In exchange they ask SG-1 to teach them how to use the gate for interplanetary travel. However, the planets they ask to visit are all gou'ald homeworlds, which are strictly off limits. When scientist Zenna Valk hints at some kind of problem with the tretonin, Teal'c and Jonas visit the facility where the drug is made and discover gou'ald symbiotes living in tanks of murky water. Dollen admits that the symbiotes, which are critical in making tretonin, have been bred in captivity by a gou'ald queen. For the drug to work, he says, the dosage has to be steadily increased. If patients stop taking it, their immune systems shut down completely. With the gou'ald Queen dying and demand for the drug growing, they Pangerans decided to procure another queen. Jonas translates the inscriptions in an underground chamber and discovers that the so-called gou'ald queen is actually the long-lost queen Egeria, the origin of the Tok'ra. A Tok'ra woman named Kelmaa breaks into the Egeria's chamber and sacrifices herself to give the dying queen her host. Egeria wakes up and reveals that she purposely passed on the imperfection in the tretonin as a defense mechanism. Realizing that the Pangerans mistreated her out of ignorance, not malice, Egeria reveals how to make the antidote and thousands of lives are saved. (Metro-Goldwyn-Mayer (MGM))