Five of Nine's origins remain a mystery, Federation records indicate a girl matching Two of Nine's general description living in the Beta Quadrant in the year 2408, but all records of her and her parents cease in 2415, she would have been 7 at the time of her disappearance.

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Five of Nine was assimilated in the year 2415, it spent 5 years inside of a Maturation Chamber, when it emerged in 2420 it was given the designation of  Five of Nine Medical Repair Drone of Unimatrix 153, its right arm had as a result been replaced with a Medical prosthesis.

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Researchers based in the Gamma Quadrant encountered Five of Nine Medical Repair Drone of Unimatrix 153 damaged but not severely on the surface of a jungle planet where the Borg Probe it was aboard had crashed, Two of Nine was the sole survivor. The researchers took Two of Nine to their Delta Quadrant base, where they were able to conduct studies and research into Five of Nine Medical Repair Drone of Unimatrix 153.

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In the year 2424 Five of Nine Medical Repair Drone of Unimatrix 153 was placed into stasis when the researchers abandoned the outpost, which is where it remained until a search team from the Delta Freedom Alliance (DFA) found it. None of the other drones kept there were active, most had been deactivated for assessment.