Long before the formation of the true Jaffa rebellion, Gerak's father began to doubt that the goa'uld were gods. When his father died at the hands of the goa'uld on Chulak, at the battle of Tazek'sur, Gerak also began to doubt the claims of the goa'uld. But, the time was not right to act on his doubts. Gerak later became the first prime of Munto (a minor Goa'uld who first served Ra, then Ba'al) and served him well. In the service of Munto, he once killed Karrok of the High Plains (first prime of Horus), who he considered to be a fool unoworthy of an honorable death. When the rebellion became strong enough, Gerak finally threw his lot in with the rebellion, and after the fall of the Goa'uld, Gerak rose to power in the new Jaffa nation. Gerak was more traditional, preferring authoritarian regimes to democratic ones. Gerak eventually rose in influence and took control of the Jaffa high council. It is suspected that, in order to gain that control, Gerak murdered Hubrock, the leader of the dispossessed forces of Ba'al, and a proponent of democracy.
Gerak was later contacted by a prior and convinced to lead the Jaffa into the Orii camp. However, when the prior insisted that Gerak use his forces to attack and destroy Jaffa that resisted the Orii, Gerak chose to stay his hand. This show of mercy caused the prior to bring Gerak's consciousness to Celestis, where the Orii evolved him into a prior. After this, the Jaffa High Council came more under Gerak's sway, while Bra'tac and Teal'c led a more determined resistance from Chulak, this time with a small fleet. Once again Gerak was forced into a position where he was to destroy those Jaffa who resisted the Orii. Teal'c convinced Gerak to meet with him on Chulak. There Teal'c made it absolutely clear that he and the Jaffa who resisted with him would die free rather than become slaves to the Orii. When Teal'c offered himself as the first to die, Gerak was finally swayed away from the Orii. Gerak went to Earth and used his prior's powers to help cure the Orii plague on Earth. This resulted in Gerak's death in a ball of flame, a safeguard that came with the powers the Orii gave him.