Jack

Jack, also known as "Subject Zero", is a notorious criminal whose crimes include piracy, kidnapping, vandalism and murder. She is also a biotic, possibly one of the most powerful human biotics alive, and considered so dangerous she was kept in stasis after she was caught. She is a potential romance interest for a male Shepard.

Jack is voiced by Courtenay Taylor.

Subject Zero

 * Rank 1
 * Health: +5.00%
 * Weapon Damage: +6.00%
 * Power Recharge Time: -6.00%


 * Rank 2
 * Health: +10.00%
 * Weapon Damage: +12.00%
 * Power Recharge Time: -12.00%


 * Rank 3
 * Health: +15.00%
 * Weapon Damage: +18.00%
 * Power Recharge Time: -18.00%


 * Rank 4 Unlocks choice between Primal Adept or Primal Vanguard
 * Primal Adept: Jack can push her biotic abilities to the limit, greatly reducing recharge times of her powers.
 * Health: +20.00%
 * Weapon Damage: +18.00%
 * Power Recharge Time: -25.00%
 * Primal Vanguard: Jack focuses her ruthless energy into combat, heightening her weapon damage.
 * Health: +20.00%
 * Weapon Damage: +25.00%
 * Power Recharge Time: -18.00%

Dossier
A young woman with a mysterious and violent past, Jack was once the prime subject of a sizeable Cerberus experiment to enhance biotic potential in humans. Referred to as Subject Zero she was the core of the project due to the success of integrating biotic enhancement into her. Many other children were also kept as part of the experiment and many died in trial runs of treatments to ensure that they would be successful on Zero. Kept separate from other children she grew up believing that the entire world was what she could see outside her window and repeatedly screamed herself voiceless while trying to communicate with others through her soundproofed cell. As they were put under the worst of the trials purely to keep Jack alive, the other kids hated Jack. This was made only worse by the fact the only time they ever saw her was when they brought her out, loaded with drugs, and forced her to fight the other children to the death to see how far she had progressed.

Eventually, while being led to another deadly test, the children panicked and rioted. Backed up by their biotics, the riot caused damage to the facility and Zero was freed. Her powers grew to such a level that she became a serious threat to the staff, easily killing one by blasting him into a wall. She would have difficulty remembering those events for the next years in her life, due to her age and the chaos. She would claim the guards and children attacked her, forcing her to kill them all. When she returned recorded logs made it more likely that the children were attempting to either get close to her for safety, as the guards had been ordered to keep Jack alive, or were trying to kill her to have some revenge over the guards and their bosses. The guards themselves were trying to kill the other children rather then Jack. No matter the true nature of events, Jack killed almost everyone in the facility and managed to get a shuttle off-world, which was picked up by another ship after several days. Exhausted from the fight and starving, the helpless girl was raped by the crew before being sold. After this the Pragia facility was shut down, though many years later the Illusive Man would claim the facility went rogue. This comes at a cost however since she is suffering from progressive neural degeneration (which is shown when you read about the implant upgrade).

Having escaped, Subject Zero went on to live a violent and bloody life. In order to sever ties with her past she took on the name Jack (though she was referred to by that name while at Pragia at times), and reacts violently whenever addressed by her former designation. She has killed various gangs, run with others, was a pirate for a while, crashed a space station into one of Kahje's moons (Dubbed vandalism by the hanar. As Jack would joke, "they really liked that moon"), and at one point was a cult member, keeping her head shaved even after her departure. Eventually, she was captured and imprisoned in the Blue Suns operated prison ship Purgatory. During her time there, she was attacked by a group of guards and prisoners who, despite her efforts at fighting back, raped her. Their victory was short-lived, as Jack personally killed every one of her attackers as soon as she healed. The incident led the Warden, who could already taste the large amount of credits Jack could bring him from Cerberus and others, to lock Jack in cryostasis, for both her and others' safety. Jack's rampage during the escape from Purgatory is the best display of her extremely powerful biotic abilities. She easily destroys three YMIR Heavy Mechs and rips gaping holes in the prison walls. No other biotics have shown this type of ability in the Mass Effect universe and Jack could arguably be the most powerful (yet erratic) biotic in the galaxy.

The tortures of her experimentation combined with her violent criminal lifestyle have rendered Jack a borderline psychopath, with a unpredictably violent nature and a fiery temper. She has an innate lust for combat, claiming to experience "warm feeling during a fight" due to her mental conditioning as a child by stimulating positive feelings whenever she fought without mercy with drugs, along with a tendency to spout profanities constantly in conversation. Her body is covered head to toe in elaborate tattoos and scars, some are remnants of her experimentation while others mark kills and major events in her life. Having been used so many times by people in her life, Jack refuses to trust anyone and is clearly angered and confused by Shepard's attempts at conversation.

Yet underneath all this she is still tormented by memories of her past and longs for some kind of closure. She joins Shepard's team in exchange for Cerberus files detailing her experimentation after which she asks the commander to help her destroy the now abandoned facility.

Loyalty: Subject Zero
After looking through her files, Jack wants to deploy a bomb at the Teltin facility on Pragia where Cerberus tortured her.

Romance
Shortly after completing the mission at Horizon, during a conversation Shepard has the option to have casual sex with Jack. If Shepard agrees, a "doing the do" scene in the small quarters on the engineering deck occurs. However, after the sex scene, Jack refuses to speak to Shepard anymore, telling him to "fuck off" any time a conversation is attempted.

Should Shepard choose to turn down the casual sex option, get to know her first, and pursue a paragon relationship, the result is very different. Jack will eventually soften up and reveal a lot about her past, where on multiple occasions she was taken advantage of when she let her guard down. She also references a time where one partner chose to stay behind rather than abandon her to die, getting himself killed in the process. He left a recording on their shuttle for her in case he died, it talked about the future they were supposed to have, how he planned to build a home for them, about how he loved her and was sorry it wasn't going to happen. This implies a great deal of "survivors guilt" in Jack, from the incident and with her escape from Pragia. She eventually tells Shepard that she needs time to think about everything; it's all very new to her and she isn't quite sure what to do. En route to the final mission, she comes to Shepard in his cabin, tells him she has been thinking a lot about him, and that he's right and she needs someone. Jack gives in, and shows a very vulnerable and emotional side. Tears roll down her face as a tender scene ensues, culminating with her smiling peacefully as they lie together on his bed as she achieves true happiness for the first time.

At some point prior to the love scene, Mordin will offer advice to Shepard in regards to his attraction to Jack, mostly concerning the fact that she is likely to either accidentally or purposefully kill him if he keeps trying to get close to her. He will offer to send information packets on biotics and mass effect field manipulation to Shepard's quarters.

Trivia

 * Jack periodically yells "I will destroy you!" and "I'll kill you!" when in combat and / or using abilities. This may be a reference to the combat barks used by humanoid enemies in Mass Effect, which became somewhat notorious.
 * Jack can become unavailable for any type of conversation if Shepard has casual sex with her, if Shepard sides with Miranda during an argument, or if he breaks off their relationship. She only replies with "Fuck off!" when approached for conversation. However only siding with Miranda will make Jack become unloyal.
 * Jack's name and shaved head might be a reference to the character Jack/Kyra from the Chronicles of Riddick movie series, more specifically the first movie Pitch Black, in which the character was approximately 14 years of age.