Sentry Mk. V

Sentry was first concieved for the Alpha universe as the daughter-clone of Ro Jackson and Rook. Her backstory remains the same in almost all universes and she generally looks like Ro (albeit a redhead, from Rook's Irish genetics), and has her abilities.

Sentry (Alpha)
Sentry's full title is Sentry Mark V. She was cloned from the DNA of Ro Jackson and Rook, as part of a project designed to create perfect soldiers from combinations of Orion Squad's DNA. Mark V is the only survivor of the project, which initially had 8 subjects (4 with Ro as the female genetic donor, and 4 with Maria as the female genetic donor).

Sentry was used by the military for black ops, until she refused to be an accomplice to the decimation of a peaceful village. She hung her commanding officer and went AWOL. Nicoli was sent to retrieve her, but upon hearing her side of the story, did not complete his mission. They remained in contact, eventually developing feelings for each other.

Their relationship was complicated by the fact that Sentry desperately wanted her own family (Rook refused to acknowledge her, and while Ro did, she did not consider Sentry her daughter), but believed she was unable to concieve. She did manage to have a child.

Sentry (Foundationverse)
Sentry's backstory is essentially the same, with expanded information on the Sentry project. The children were kept together, even though some were mentally unstable, and were not told that they shared DNA (meaning that each child had four half-siblings). Maria and Fox's 'son', Mk VIII, did figure out that Mk VII (Fox x Ro) was his sister, as they shared their 'father's skin tone. Of the original 8, Mk. V and Mk. II (Isaac x Maria), were the favorites of the research staff. After Mk. II raped VII (causing her to kill herself) and killed Mks. I (Sage x Ro) and IV (Rook and Maria), one of the researchers referred to him as an agent of Darwinism, weeding out the weaker Sentry subjects. V took leadership of the group, trying to keep the remaining subjects from being left alone with II. II was eventually killed by VIII, out of revenge for his sister (not knowing that II was actually his brother). With four remaining, the Sentry subjects were sent out on missions. III and VI were killed in action early on, and VIII was terminated. V, the remaining Sentry, was placed into stasis by Promethesus Labs, and eventually found by the Foundation.

Sentry was placed in the care of Fiona and Aleksei. Though Fiona offered to have her name changed to whatever she wished, Sentry only knew that name and continued to go by it. Fiona and Aleksei invited their son, Nicoli, over for dinner often so Sentry could have some normal interaction. Fiona quickly worried that Nicoli would develop deeper feelings for Sentry, and Sentry would not know how to respond. Though she would prove to be correct about the former suspicion, Sentry asked Nicoli if she could work for the Foundation as an agent. She proved to be a very useful tool, though Ro Jackson did not acknowledge her.

When Ro Jackson was kidnapped and tortured by Serpent's Hand, the Foundation discovered that clones had been made of her. Sentry adopted one of the child clones (as did Ada Wong), and when told that she would have to severely compartmentalize her life in order to keep Ro and the Foundation a secret from her child, chose to leave the Foundation (although Nicoli remained an agent).

Sentry (Metal Gear Universe)
Sentry was a member of the Beauty and the Beast corps, codenamed Quiet Fox. As a child, she lived in Central America, and was a child soldier, one of many who were all called Sentry. She led many American soldiers to their deaths by pretending to be a quiet, shy girl, then stealing their things and leading a chase that ended in an ambush. She never directly killed anyone, but carried much guilt about this. Her suit was a variant of a sneaking suit equipped with cybernetic enhancements and a cyborg exoskeleton which greatly enhanced her agility. The back also segmented into several 'tails' that could produce electric shocks, giving her the appearance of a nine tailed fox.

Unlike the rest of the BB corps, she had no desire to kill Solid Snake (Nicoli) and instead led him on chases around Outer Haven, often accidentally leading him to other members of the BB corp. When fighting soldiers, she would use nonlethal means of incapacitating them, which led Snake to believe she did not want to kill anyone. He incapcitated her and brought her back to the base for psychological evaluation.

It was determined that Quiet Fox was not a threat and was allowed to remain on base and work for them. It was noted that she wandered the base in distinct patterns, as if on a patrol. This was a remnant of her cybernetic implants and their patrol instincts. Her patrol was based around the likely location of Siela, who she would check in on, and often turn down the stove so she did not burn food. She did not speak often, but about 1/3 of the time she would ask about Nicoli. When finally allowed to see him, she stayed with him until he died, promising to watch after Otacon (Eli) and Siela.

The personnel on base were often unnerved by Quiet Fox's patrols, and found it unsettling how attached she was to Siela. This was worsened when Siela built Quiet Fox a new cybernetic sneaking suit with OctoCamo, making Quiet Fox almost undetectable.

During one mission, Quiet Fox was targeted for a Honeypot by an enemy agent named Sam. Knowing she had loved Solid Snake for saving her life, he emulated the legendary agent and seduced her. When he attempted to kill her while she slept, her suit detected him as hostile and attacked on it's own. Sentry discovered that Siela had programmed it to do so, as well as sending information back to the base and monitoring her vital signs. Sentry was momentarily concerned that Siela had witnessed her and Sam's intercourse, but Siela had only been alerted after the suit had determined she was in distress. Quiet Fox completed her mission even though the enemy knew she was there, what she looked like without her suit, and her real name (Mariana Diaz).

When she returned, she was more withdrawn than usual, speaking only to Siela and Yurik. She felt that the other personnel had lost what little respect for her they had, knowing she was seduced and almost killed.

Trivia
Sentry is not named after the Sentry from Marvel comics, but rather the song Key Entity Extraction V: Sentry the Defiant by Coheed and Cambria. In the song, a soldier named Sentry is horrified after a village is wiped out by his commanding officer. When he attempts to expose his cruelty, his CO hangs him. A sentry is a soldier. Sentry is one of a few characters inspired by and named after Coheed and Cambria.

Sentry's speech pattern greatly differs in the MGS universe from her other incarnations. In the MGS universe, she speaks in short sentences (often four words or less, sometimes just one word answers). She leaves out pronouns often, as well. After Solid Snake's death, 75% of her interactions are with Siela. The rest are divided mostly between Otacon and Yurik.

She is also mostly inspired by Gray Fox (even though Khione is the Gray Fox for tht universe), rather than her corresponding BB corp character or the characters that the BB corp themselves are inspired by. Sentry is also the only BB corp member to survive, the other three are killed by Solid Snake (though Sentry did not care about them). Like Solid Snake, Quiet Fox possessed a forgiving nature.