A civilian diplomat and the first commander of the Atlantis expedition in the Pegasus Galaxy. An expert in international politics, Dr. Weir is well-known for mediating for the United Nations. When President Henry Hayes took office in 2004, he placed her in command of the S.G.C. after moving General George Hammond to a new position. After standing up to Vice President Kinsey and his agenda to take control of the Stargate program, Weir led a total review of the Stargate program over the following months.
Upon the promotion of Jack O'Neill, Weir was transferred to the Ancient outpost of Atlantus, left behind in Antarctica when the city of Atlantis left the planet between five and 10 million years ago. When Daniel Jackson discovered the Stargate address for Atlantis, Weir led the pioneering team through the gate.
Weir's work in diplomacy was referenced by Dr. Jackson when drafting the initial treaty for the Tok'ra-Earth alliance. She speaks five languages, including Russian and Latin (the latter of which is very similar to Ancient). Weir brokered a dozen of the most sensitive international treaties in modern times, and President Hayes used her mediation in North Africa to sway her into her new job.
Weir originally had an aversion to the military, having started her career as a political activist lobbying against government spending on the military. She concluded that, in her own words, the best way to stop the proliferation of weapons is to try and end the need for them. But when she was assigned to the Atlantis expedition, she was in a position of authority over the base's military contingent.
Elizabeth left behind on Earth at least one person very close to her (in addition to her dog, Sedgwick): a man named Simon Wallace. When she managed to return to Earth after a year of being out of contact, she learned that Simon had met someone else and their relationship was over.
Weir returned to Atlantis, where she continued to face difficult ethical and military situations on a regular basis. Though her inclination is always to seek a diplomatic solution to conflict, she has been forced to realize that this usually is not possible when facing ruthless enemies such as the Wraith and the Replicators – enemies who threaten human existence itself. But she has had more success with others, including the Genii.
After three years as commander of the expedition, during which she also faced questions about her leadership from the I.O.A. (the governing body in charge of the expedition), Dr. Weir was critically injured as Atlantis fled a Replicator satellite weapon. Her brain swelling and her body near death, the team's only choice was to reactivate the Replicator nanites that had infected her a year earlier. Rodney McKay reprogrammed them to heal her body – but rather than regenerating organic cells, the nanites are now integrated into her system. She is part Replicator.
This allowed Elizabeth to access the Replicators' collective consciousness and lead Sheppard's team on a daring mission to save Atlantis. Elizabeth herself confronted the Replicator leader, Oberoth, distracting him long enough for her people to escape – though she herself had to remain behind.
When the team encountered a Replicator-made double of Elizabeth several months later, they learned the probable fate of their friend: Oberoth had her executed. The double herself was killed (along with doubles of Sheppard's team) saving them.
Lost City, Part 1 - Weir travels to the White House, where the new President offers her the job of leading Stargate Command.
Lost City, Part 2 - Weir continues to hold her ground at the S.G.C. despite the fact that Vice President Kinsey is demanding the gate be opened to send him clear of Earth.
New Order, Part 1 - As the new commander of the S.G.C., Weir must negotiate with the Goa'uld System Lords when they arrive seeking an alliance against Baal.
New Order, Part 2 - Weir and Jackson must avoid Goa'uld invasion when their negotiations with the System Lords go south.
Rising, Part 1 - Weir is overjoyed to discover that the lost city of Atlantis is located in the Pegasus Galaxy, and mounts a team to travel between the two galaxies to learn what lies beyond.
Thirty Eight Minutes - Elizabeth must stand up to challenges to her authority from both the Athosians and the scientists from Earth, as they struggle to save the team trapped in a Puddle Jumper that is lodged in t
he Stargate. Suspicion - Weir's authority is put to the test when she must interview the Athosians, in search of a possible traitor.
Poisoning the Well - Faced with the potential of finding a way to prevent the Wraith from feeding, Weir decides to allow an experimental drug to be used on a Wraith prisoner.
Home - Weir returns home and is reunited with her lover Simon, only to discover that the entire trip is an alien facade.
Before I Sleep - When a severely aged Weir is discovered in stasis in the city, the team learns that she traveled 10,000 years into the city's past and saved all their lives.
Letters From Pegasus - On the eve of a Wraith attack, Elizabeth records a personal message to Simon, telling him to move on.
The Siege, Part 2 - Relieved of command by a new military officer from Earth, Elizabeth risks her life to negotiate with the Genii for use of their nuclear weapons.
The Intruder - On a trip home to Earth, Simon tells Elizabeth that he has met someone else.
Condemned - Weir joins the team off-world to negotiate with the Olesians, but learns that the Magistrate does not have her people's best interests in mind.
The Long Goodbye - Weir is taken over by an alien entity, who is at war with another entity that possesses Colonel Sheppard.
Michael - Weir gives the OK to use Dr. Beckett's Wraith retrovirus on a prisoner, and attempts to convince "Michael" that he is one of their own people.
Allies - Dr. Weir strikes a tenuous bargain with a Wraith Queen, knowing that it is almost certainly a trap.
Progeny - Weir attempts to negotiate an alliance with the most advanced people the team has ever encountered, only to learn that they are human-form Replicators.
The Real World - Infected with Replicator nanites that threaten to kill her, Elizabeth dreams that she is back on Earth – a fragile psychiatric patient who dreamed up Atlantis and the Stargate.
The Return, Part 1 - When a group of Ancients return to Atlantis and force the team to return to Earth, Weir keeps her friends at arm's length and becomes increasingly reclusive.
Sunday - Elizabeth toys with the possibility of a romantic relationship with a member of her expedition, but eventually pushes him away.
First Strike - A Replicator attack on Atlantis leaves Elizabeth critically injured.
Adrift - Dr. Keller fights to keep Weir alive, but only a risky plan to reactivate the Replicator nanites still her system saves her life.
Lifeline - Now part Replicator, Elizabeth plays a vital role in helping the team infiltrate the Asuran homeworld to save Atlantis. She goes head-to-head with the enemy leader, Oberoth, but must finally stay behind in order to help the team escape.
This Mortal Coil - A Replicator duplicate of Weir and the rest of the team turns up, fleeing from Oberoth's forces – and sacrificing themselves to help the real team escape.
Be All My Sins Remember'd - In the wake of the destruction of the Replicator homeworld, a version of Weir – most likely a Replicator copy herself – leads a ship full of survivors.
Ghost In the Machine - Having lost her Replicator form to a failed experiment in ascension, the Weir duplicate comes to Atlantis and reincarnates herself in the body of Fran, finally sacrificing herself to keep the city safe from the rest of her kind.