Goa'uld who once possessed the body of Vala Mal Doran. Qetesh ruled over at least one world, P8X-412, where she forced the inhabitants to mine the planet's sparse naquadah deposits. When quotas were not met she instituted both mass executions and mass torture.
Qetesh had shared a romantic "spark" with Baal, and she took great pleasure in meddling in his plans. She once attacked his fleet at Selenis, crippling his flagship and killing ten thousand of his best Jaffa.
Despite their tumultuous relationship, Baal installed Qetesh (in the host of Vala) as his queen when he traveled over 80 years into the past and altered the timeline to suit himself.
Qetesh disagreed with Baal's uncharacteristic approach on how to win over the Tau'ri when the Goa'uld arrived to enslave Earth. He overruled her when she suggested a more direct, mass-murder approach than the gradual takeover Baal proposed. The moment the opportunity availed itself she impaled him with his own blade and instructed the fleet to bombard the planet in the name of the sovereign.
Qetesh then set a course for Praxion, the planet where Baal's time machine was kept, and used ring transporters to transmit her army to the surface and eliminate SG-1, who had hoped to use the device themselves. When Qetesh arrived Teal'c, the First Prime of Baal, avenged his master by murdering Qetesh with an explosive.
The Powers That Be - Vala, posing as Qetesh, returns to P8X-412 to recover her treasures and warn the population about the threat of the Ori.
Stargate: Continuum - A change in the timeline allows Qetesh to be reborn at the right hand of Baal.