Replicator Carter, also known as Replicator Sam, was a Human-form Replicator created by another human form replicator known as Fifth in the image and also physical appearance of Samantha Carter.
Although Fifth intended for her to be his consort, Replicator Carter later rebelled against Fifth and upon his death, became the new leader of the Replicators.
For over a year and a half, Replicator Carter also led her fellow Replicators into battle, came close to seizing total control of the entire Milky Way galaxy, and killed many Goa'uld System Lords, up until her own eventual death in 2005.
Like other Human-form Replicators, and standard Replicators for that matter, Replicator Carter was solely constructed from the conjoinment of a large number of identical Replicator "blocks". Human-form Replicators, as their name suggests, take perfect human form, and are composed of much smaller blocks (i.e. nanites) than standard Replicators.
She was made in the real Major Samantha Carter's image, even right down to the original's own memory and character despite Replicator Carter herself acknowledging that they were not hers.
The information used to create Replicator Carter was probably collected during Carter's temporary imprisonment on Orilla at Fifth's hands. However, the differences between Samantha Carter and Replicator Carter became quite pronounced due to Fifth's training of the latter which had Replicator Carter going through various scenes which ended with her killing her own original self's colleagues and friends in cold-blood.
This over time resulted in Replicator Carter becoming a megalomaniac, ruthless, dominating conqueror with a strong thirst to achieve power by any means while also growing to hate Fifth for his actions. She also believed that these traits were also within the original Samantha Carter, as "all humans desire power". According to Replicator Carter, the only difference between the two is that Samantha never had the bravery, or means, to act upon it.
Like all Human-Form Replicators of her kind, Replicator Carter was immune to both projectile and energy weaponry. She possessed the ability to reform herself at any time, not only to heal herself but she could also reshape her arm into a weapon so that it resembles a long sword, with which to kill enemies as seen when she murders Lord Yu and Dr. Daniel Jackson..
She could also deactivate portions of herself, effectively enabling her to leave parts of her body behind. Replicator Carter was also connected to the Replicator data-stream called "The Link".
After the android Reese was used as bait by the Asgard to trap all Replicators in the known universe inside attime[1]dilation field, the advanced technology, including the nanites within Reese's systems, were studied by the approaching Replicators. Based upon these nanites, the first human-form Replicator could be constructed. However, Reese's programming was flawed, which was also discovered by the Replicators, who attempted to correct the error in the creation of Fifth. As a result, Fifth was both the first and the last human-form Replicator created with the capacity for emotion, as the others came to see the feature as a flaw. This led to Fifth falling in love with Samantha Carter, and when he realized he could not have a relationship with her in the form he desired, he created a perfect replica of her which he hoped would accept him. Fifth intended for Replicator Carter to govern the Replicator race with him, and to be his consort. Due to his infatuation with Samantha, he made her exactly in her image, down to her memories and character. However, this in part led to her despising what he was trying to do as much as the original Samantha Carter would have. (SG1: "Menace", "Unnatural Selection", "New Order. Part 1", "New Order. Part 2")
2004 After Colonel Jack O`Neill had engineered a weapon able to disintegrate any Replicator in its blast-radius (the Replicator distuptor) based upon Ancient knowledge, the Replicators's quest to control the Galaxy had reached a dead end. In the meantime, Replicator Carter was able to fool Fifth into believing that she was loyal to him, and maybe even shared his love when in reality, she was manipulating him. The two eventually devised a plan to discover how to immunize their race from the Replicator disruptor. The plan involved sending Replicator Carter to Stargate Command, claiming that she had betrayed and fled Fifth, and expressing a wish to be destroyed by their Disruptor. SG-1 took her to the Aplpha Site to question her, where she informed them (untruthfully) that Fifth had immunized every single Replicator to the Disruptor, except her due to his spite. However, she promised to help them realign the Disruptor to overcome Fifth's immunization. As they began work on the Disruptor, Replicator Carter was able to study the weapon to discover how to immunize her race from it. She relayed reports of her progress back to Fifth, keeping in communication with him via the data-stream between all Replicators.
Unbeknown to the SGC and SG-1, Fifth was tracking her position, on his way with one of his powerful Replicator ships to attack the planet, confident Replicator Carter would upload the cipher to render the Disruptor useless before he arrived. However, Replicator Carter eventually betrayed Fifth by firing the Replicator disruptor sattelite at his ship before she uploaded the cipher. Both he and his ship were destroyed, before Replicator Carter immunized herself and her race. Teal`c attempted to stop Replicator Carter by grabbing her arm, but the arm detached from her body and she escaped via the Alpha Site's Stargate. Carter's attempt to violate Brigadier General Jack O`Neill's orders to terminate Replicator Carter played something of a major factor in her escape. The arm removed by Teal'c decomposed into deactivated cells which were studied by Carter, who felt personally responsible for her Doppelgänger's victory. As a result of Fifth's destruction, Replicator Carter subsequently took over the vacant position, eventually gaining full control of the entire Replicator race. (SG1: "Gemini").
2005
Several months later, Replicator Carter led her army back to the Milky Way, and launched a massive attack on the Goa`uld, taking over their territories and incorporating their technology into her own. She first paid a visit to a summit of System Lords gathered at the Hasara space station which she achieved by disguising herself as the original Samantha Carter. Upon revealing her true identity, she began killing all of attendees of the meeting. Among the victims were Lord Yu and his First Prime Oshu, Ba`al's representative with her Jaffa and two Kull warriors, and two unidentified Goa'uld with their own first primes.
Knowing of the ascended knowledge still present in Dr. Daniel Jaskson`s subconscious mind, information that could possibly be a threat to her invasion, Replicator Carter captured her original self's teammate and tricked his mind into believing she was Oma Desala again offering ascencion. He thereby opened his mind to her, revealing things that he wasn't aware of, including a weapon capable of killing her and the other Replicators.
After hours of probing his mind, Replicator Carter discovered the weapon was situated on the planet Dakara known as the Dakara Superweapon, a device that, when altered, could be used to destroy her entire army at once. However, the Replicator invasion, seen by many Jaffa as holy retribution for their blasphemy against their Gods, proved not only to be disastrous for the Goa'uld, but also caused many rebelling Jaffa to revert to their old religion. Teal`c and Bra`tac, along with many Jaffa, subsequently attempted to take over the Temple of Dakara, an act that they believed would prove to all Jaffa that the Goa'uld are not gods.
Replicator Carter sent her forces to Dakara to eradicate the weapon, engaging the Jaffa rebels and Ba'al's fleet, who had turned his fleet on Dakara to drive out the Rebel Jaffa. Luckily, though, the real Lt. Colonet Samantha Carter and her father Jacob Carter had also discovered the weapon, and recognized it as the only thing capable of destroying the Replicators, since it was based upon the same technology as the Replicator disruptor. The Replicators eventually landed on Dakara and attempted to reach the weapon.
In the meantime, Daniel, while allowing Replicator Carter to enter his mind, was able to work his way into her mind and entered in a mental duel with her, and was able to momentarily freeze every single Replicator in the galaxy, including those on Dakara and those invading Stargate Command, using some of the knowledge of the Ancients that she helped unlock.
However, she regained control of the Replicators soon afterward, and explained to Daniel that his mind was simply not capable of controlling all of the Replicators at will, even though he had the knowledge to do so.
Recognizing Daniel to be a threat, Replicator Carter stopped probing Daniel's mind and caused her own right hand to develop into a sharp blade before using it to stab Daniel through the chest which killed him instantly although Daniel later returned with help from The Others.
With Daniel's distraction, the real Lt.Colonel Samantha Carter, with the help of her father, Jacob Carter/Selmak and Ba`al, were able to reconfigure and program the weapon to send out massive shockwaves that would cause only the Replicators to permanently disassemble.
These waves were spread over throughout the entire galaxy via every working Stargate, destroying all Replicators in the Milky Way galaxy, including Replicator Carter herself.
All Replicator Carter could do was look on in horror as she and her ship were destroyed by the weapon seconds later, finally ending her regime as well as that of her fellow brethren for good. (SG1: "Reckoning. Part 1", "Reckoning. Part 2").
Stargate SG1 - Twins Death of Fifth HD