- "This is Colonel Lionel Pendergast of the Earth vessel Prometheus."
- ―Lionel Pendergast[src]
Lionel Pendergast was a male Tau'ri who served as Colonel in the United States Air Force. He replaced Colonel William Ronson as commander of the Earth vessel Prometheus sometime after the ship's return to Earth from Tagrea.
Over a year later, during a mission to rescue SG-1 member, Dr. Daniel Jackson, an Ori satellite attacked the Prometheus, triggering a battle which eventually ended with the Prometheus itself being destroyed, resulting in Pendergast being killed in the explosion although he was ultimately hailed as a hero for saving seventy-six people associated with his crew, key personnel being Major Kevin Marks, Lt. Catherine Womack as well as SG-1 members, Lt. Colonels Cameron Mitchell and Samantha Carter and also Teal'c of Chulak.
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, only to stop when they received a transmission from Teal'c of Chulak. (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 later, 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 even 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 manned the Prometheus for its final mission during the attempt to rescue Daniel. Unfortunately, they came across an Ori satellite belonging to the Rand Protectorate which lay above Tegalus with Prometheus attempting to destroy the satellite but failing. The satellite then attacked, dealing incredible, almost overwhelming damage to the ship while even damaging the hyperdrive, preventing them from escaping. To buy Carter time, Pendergast offered to surrender to prevent the satellite from attacking the ship but President Nadal rejected Pendergast's suggestion. With no other options left and time having run out, Pendergast gave the order to abandon ship, remaining on board to ensure the safe evacuation of his crew using the Asgard transporter. Seconds later, the satellite struck, its final shot managing to cause Prometheus to split in two with the explosion killing thirty-nine of her personnel as well as Pendergast himself although Pendergast's leadership was credited with saving the lives of two-thirds of his crew. In the aftermath, Mitchell who had served with Pendergast later personally hand-delivered Major General Henry Landry's letter to Pendergast's wife and children. (SG1: "Ethon")
- Was later revealed to be married with a wife and kids although his wife's name was not revealed nor was it revealed how many children Pendergast had.