The Simulation Goa'uld is a Goa'uld created in the simulation Teal'c experiences through the virtual reality pod. It works as an infiltrator for Ba'al during a Kull warrior attack on Stargate Command.
During the simulation Teal'c experiences through the virtual reality pod, the game changes to include the addition of a Goa'uld infiltrator. While the Kull warriors attack Stargate Command, the Goa'uld uses the diversion to destroy the base either through the self-destruct or overloading a naquadah generator. If one method is stopped, the Goa'uld activates the second method. In the first simulation with the Goa'uld, it takes Dr. Daniel Jackson as host and shoots MSgt. Walter Harriman zats to prevent Teal'c from sending the overloading generator through the Stargate.
Teal'c subsequently comes to believe that the Goa'uld is the final challenge of the game and it must be defeated to win. However, the identity of the Goa'uld's host changes to make this harder and its identity doesn't become clear until the last second. On several occasions, the Goa'uld's host is Daniel. As a result, when the real Daniel enters the game, he's killed twice by Teal'c who believes Daniel to be the Goa'uld until Daniel zats Teal'c to force him to listen. Teal'c then explains about the Goa'uld and its role in the game.
In the final simulation, after taking out the Kull warriors, Teal'c and Daniel head to a storage room where they find Lt. Colonel Samantha Carter with an overloading naquadah generator and an apparently dead MSgt. Sylvester Siler lying nearby. Carter claims that Siler was actually the Goa'uld and that she is able to stop the overload if they let her. The situation devolves into a tense standoff between Carter, Teal'c, Daniel and Brigadier General Jack O'Neill before Teal'c agrees to let Carter stop the overload.
As Carter works on the generator, Daniel has a two-second premonition showing Siler sitting up and attacking. Daniel warns everyone in time to avoid the attack and Teal'c kills Siler, who was in fact the Goa'uld, with an FN P90 Personal Defense Weapon. With the Goa'uld dead and the overload stopped, the game ends. (SG1: "Avatar")