Mercury was born outside of the world of Equestria as a human... Or a human-like being, rather... She was actually born to a lineage of demigods and demigoddesses. Both of her parents carried that gene. Because she decended from a particular family, she is endowed with the will of the goddess Vermilion. There is a lot of story to go through here, so buckle up, and be prepared for tl;dr syndrome...
Mercury Halynn is a strong-willed and respectable young woman born into a life of hardship in Clayton Bay. Her father, Viktor Halynn, was a former member of the Mafia that once controlled her now-forsaken hometown. Mercury revered her father as one of the greatest human beings ever to walk the face of this planet, regardless of his past affiliations. Everything she is now is a result of her father, who raised her and her brother to be as resilient as they are today. Viktor was his daughter's hero, however, he did not live to see his daughter grow up and free his former home. Mercury had to witness the ruthless murder of her parents at the young age of 16. She has never forgotten who issued the order for the hit, and she spared no efforts in taking revenge ten fold on her father's so-called "family." Before this tragedy, she was perfectly normal. She was your average sophomore in high school. She was a well-endowed student, a gifted musician, and a talented artist. Before her father's murder, she had a perfect 4.0 GPA. But her parents were not the only thing taken from her during those hard-fought years in Hell. She, her brother, and their 3 closest friends; Jayden Raux, Allesana Skye, and Micheal O'Hara, spent years fighting against the Mafia with equal brutality. Throughout those years, Mercury developed a sort of bloodlust, an inceaseable desire to take absolute revenge on the Mafia. Then arose a serious problem. After successfully carrying out the hit on Viktor, the Mafia found out about his personal connection, and the entire Halynn clan was targeted. One by one the Halynn family was being slaughtered for their connection to Viktor, and since Mercury and the gang were responsible for many deaths of important members of the Mafia, there was a massive prize for collecting their heads. The Mafia boss's exact order was, "Bring me their heads. I don't care what you do with them before hand, just make damn sure that these little shits go in the most painful of manners." Mercury was the first of the group to be found. Mercury is a good looking girl. In school, she was constantly and effortlessly snagging the attention of every guy who could see her from where they were standing, and the hit squad that found her was no different. In which case, they decided to take the liberty to do what they will before they dispatched her and collected the bounty. Mercury was trapped, bound, beaten within an inch of her life, and then raped. When she regained consciousness, she found her self completely stripped, chained to a steel pipe in some arbitrary alley, bleeding profusely from various lacerations, and dotted with the hit squad's...*ahem* 'excretions.' Terrified, alone, and staring into the face of her demise at such a young age, she could feel the tears working their way up. But, her body simply refused to let her cry. She sat there, battered and beaten, chained naked to a pipe, knowing what had just happened to her. Yet, she simply wouldn't break, though she could still feel the bottomless abyss of shame and sorrow dwelling in her heart. At that point she realized that her assailants were still lingering, debating whether to kill her now or to use her more, like a group of demented children arguing about what sick, twisted game to play next. The sorrow she felt quickly developed into a burning, uncontrollable rage. While the 5 Mafia members fantasized about what else to do with her body before offing her, Mercury was being consumed by a hatred that lit the very fires of Hell burning in her eyes. By the time they realized she was awake again, she had broken free of her restraints, and was giving them a glare that would shake even Satan himself to the core. The Mafia lost it's 5 strongest soldiers that night, slaughtered mercilessly by a girl that was something inhuman. It turns out that the previous statement is strangely accurate. Mercury was born a being that later became known as "Arian," a race of mythical people who were descendants of god-like beings, and she's not the only one. Her brother was born with that same blood. Mercury was shocked, and slightly frightened of her new-found super-human capabilities. This provided a whole new means of fighting her most hated enemy. However, this did not mean that the consequences of rising against the family were eliminated. During one particular raid on a Mafia stronghold that didn't go quite as planned, Mercury's first love, the character Micheal O'Hara, was captured and given a public execution. Once again, even despite her immense power, Mercury was unable to save a loved one. Now, for the first time since her father's murder 3 years ago, she was in absolute, blinding emotional turmoil. For the first time in 3 years, she cried, screaming in unparalleled anguish as though her heart was literally being ripped from her body. As she screamed out in her deafening sorrow, what was left of her mind was shattered; she lost control. In a horrifying act of desperation mixed with insanity, Mercury, alone, waged war against the Mafia's 1300 remaining members. Her friends and brother couldn't bring themselves to watch Mercury engage in an all-out war with suicidal abandon. Despite their efforts, they couldn't block out the sounds of what they thought was Mercury being torn to shreds by the Mafia's heavily armed war force. Just as suddenly as it began, the gunfire ceased. As the rest of the team of young vigilantes braced themselves to witness their comrade's tattered, bloody remains, they found themselves both relieved and terrified at the same time. There Mercury stood, in the midst of an entire legion of gruesomely slaughtered Mafia soldiers, her entire body drenched in the blood of her enemy. What scared her comrades was not that she so ruthlessly slaughtered the Mafia, as they would've done the same thing provided they could have, but rather the look on Mercury's face. Her contorted expression gave away the mental scars. She had fallen to her knees, staring intensely at the blood on her hands, tears pouring down her cheeks. One corner of her mouth twitched rapidly so that her expression quickly switched between a manic grin and a look of overwhelming terror. Even after intensive therapy Mercury still can't let go of that image. Though she has recovered enough to hide her scars at the very least, she has suffered mental and emotional wounds that will never heal, and the actions she chose will haunt her for the rest of her life. Her friendly disposition is starting to return, and she tends to be in high spirits nowadays, though she still suffers from random bouts of depression.
Okay, that's how it all started. Eventually, Mercury faced off against her most hated enemy, the boss of that mafia family that took everything from her, Malchovich. He is also a member of Mercury's race, and is among the strongest of them. He is infact so powerful that Mercury's only hope against him was the will of the goddess she decended from, Vermilion. Ultimately, she defeated Malchovich, saving the world, and likely the universe as well. At last she could be at peace. She wandered away from the battle, dropped to her knees, layed down, and died. Her astral body floated through the plains of existance, searching for a suitable realm to take presence in. Ultimately, she appeared in Equestria. She materialized in a forest, extremely weak and extremely vulnerable. A couple of minutes after her arrival, she was found by Nimble Wing (another member of AOS), who nursed her back to health. 5 years passed between now and that meeting, and that time has forged a friendship stronger than most could know.
More About Mercury
Mercury is friendly, but normally soft-spoken and shy. Certain events that have occurred in her life have caused her to become particularly wary of men. Her resolve is strong, though. When her mind's made up, her mind is made up, and nothing will stop her from doing what she feels must be done. She has a short temper, and can become quite violent when angered. Mercury's cutie mark is a cracked heart of stone being held together by a golden triforce with an angel wing on the left side. This represents her talent for peering into the hearts of others, which she uses to try to help mend another's broken heart. She has helped many bounce back from depression, and has prevented suicide in some cases. Mercury has a long standing friendship with the OC Nimble Wing, and is therefore usually involved in stories regarding said character.
Mercury is an extremely talented guitarist and vocalist. She spends much of her time nowadays practicing her guitar. Growing up with her father, who was also a musician, she developed a life-long, almost obsessive love of music. She sometimes would even go so far as to call music a turn-on.
Just how powerful is Mercury? The most she can lift with her arms exclusively is 28 tons, and that's in her standing state! In her enhanced power state, tier 2, powered by the will of Vermilion, her strength doubles, and her speed nearly triples! Though, there is a dark side to her... A side that was born of losing her first lover. It's called the third tier of Vermilion... Corruption. In this state, she is more vulnerable, but her strength is multiplied by 1.5, and her speed is 4 times that of her normal state. In this form, she has no moral restraint, and an insatiable bloodlust. This form is triggered by negative emotions, and will behave differently depending on what triggers it. If it is triggered by rage, she is a mindless killing machine, and will destroy everything in her way. If triggered by sorrow, she will set one target, the one who has caused her the most pain, and stop at nothing to make them pay. A stress trigger takes some time. The more build-up of stress, the stronger that tier gets until she is consumed by it. She becomes a demented, murderous version of herself.
The Absolutes; The Absolutes are the true deities from which Mercury's race descended. Each of the Absolutes takes the form of some aspect of nature. The Wind, The Water, The Earth, The Fire, and The All-Being. The All-Being is the source of everything in nature that isn't already a part of the other Absolutes. The lineage of the Absolutes began with the All-Being, giving birth to the second race known as the Guardians.
The Guardians; The Guardians are appointed the task of defending the creation of the Absolutes from any threat of a power greater than the naturally developing inhabitants. Each of the Guardians represent a different human element. For example, Vermilion is a representation of the strength and beauty in freedom. The aspect that Vermilion embodies will be what leads to the end of the Guardians, and the beginning of the Will of Vermilion.
Vermilion; The story of Vermilion's struggle has been passed down through hundreds of generations. The will of her strength is a legendary power, said to have died out long ago, that has been revived in Mercury. (The actual story will be added as soon as the final touches are added. Just a quick update for everyone.)