|Out of universe information|
- "This is Colonel Lionel Pendergast of the Earth vessel Prometheus."
- —Lionel Pendergast
Following Anubis's destructive assault on Earth, Pendergast and the Prometheus were given the uneasy charge of patrolling the planet for fear of Goa'uld aftershocks following the battle. During the course of this mission, Pendergast intercepted Thor's Asgard mothership, the Daniel Jackson,when it arrived in Earth's solar system, at first believing it to be a possible threat. (SG1: "New Order, Part 2")
Some time later, he conducted the search for Osiris' Al'kesh in orbit of the planet. When that ship, after being infiltrated by SG-1, attacked the Prometheus, Brigadier General Jack O'Neill hesitated to allow Pendergast to return fire; however, his crew managed to transport the Stargate and SG-1 aboard before the enemy vessel entered hyperspace. (SG1: "Endgame")
Several months, Pendergast was sent to pick up SG-1 on P4C-452 and head to Kallana to deliver a Mark IX Nuclear warhead to the Ori beachhead. He maintained the ship's position when the Jaffa Gerak and a fleet of Jaffa motherships arrived to assault the force field, and when the Ori attempted to initialize their Supergate. (SG1: "Beachhead")
Later the Prometheus was called in to help find a Goa'uld Naquadah bomb that was so powerful that evacuating five miles wouldn't be enough. The crew transported Lt. Colonel Samantha Carter from Maryland to Seattle and then beamed her team out before the bomb went off. At the last minute, Lt. Colonel Cameron Mitchell came up with a plan and contacted Pendergast and had him beam the building that was the bomb into space where it exploded harmlessly. (SG1: "Ex Deus Machina")
Pendergast was on board the Prometheus when it was lost to an Ori weapon satellite above Tegalus. After the ship was rendered defenseless and his offer of surrender was rejected, he gave the order to abandon ship, remaining on board to ensure the safe evacuation of his crew using the Asgard transporter. He was killed when the ship was ultimately destroyed, but his leadership was credited with saving the lives of two-thirds of his crew. (SG1: "Ethon")