“Seth” is episode two of season three of Stargate SG-1.
Sam’s father, who is now one of the Tok’ra after he joined with Jolinar in “The Tok’ra: Part 2”, has come to Stargate Command with news that the Egyptian deity Setesh, also known as Setekh or Set, a Goa’uld System Lord (and generally considered to be a fairly unpleasant type), is believed to have never left Earth when the Egyptian stargate was buried, and is still there hiding somewhere.
Both Ra and the Tok’ra wanted Set dead (Mister Popular he wasn’t), so he was probably hiding out. Given the Goa’uld predilection for setting themselves up as gods and using religion, it seems likely that he will have done something like that. Daniel starts tracking Set’s cult through history.
Set, or Seth, is running a heavily armed religious cult outside Seattle, and SG-1 go to investigate.
An episode set entirely an Earth, and another one that I don’t remember. Set was one of the more important figures in Egyptian mythology. In comparison, this one’s a bit pathetic.