Shak'l (Skak'l in end credits of The Nox) was a Jaffa in the service of Apophis. When Apophis went to hunt the fenri on Gaia, Shak'l accompanied him. He was killed when SG-1 attempted to capture Apophis, but was revived by the Nox. Teal'c, his former instructor, tried to convince Shak'l that the Goa'uld were not gods, but Shak'l refused to listen. He killed Lya during his escape, but Apophis and the other Jaffa were sent back through the Stargate. (SG1: "The Nox")
Later, he lead a group of Serpent Guards to Cartago. Shak'l found a captured Teal'c, who was to be executed that day by the Byrsa. Shak'l was convinced that Teal'c's death would insure his place as First Prime, but Teal'c stabbed Shak'l in the symbiote pouch, telling his former apprentice that he was sorry. (SG1: "Cor-ai")