Jaffa in the service of the Goa'uld Baal. Til'Vak was responsible for administering the brainwashing device to various members of the Jaffa High Council on P2M-903, in order to sway them to his master's plans for preventing the Ori from entering the Milky Way Galaxy at all costs.
When it came time for him to break Teal'c, Til'Vak discovered the device would not work on him. Teal'c had previously been brainwashed by Apophis and had overcome it with the Rite of M'al Sharran. Instead, Til'Vak had to hand the subject over to Baal for further interrogation.
Til'Vak was made to believe that he succeeded in breaking into Teal'c's mind, but the Jaffa was playing a mind game of his own until the right moment to strike back at his captors.
Stronghold - Til'Vak takes pleasure in using the brainwashing device for the plans of his master, Baal.