There are a few, perfect, notable, calculable moments in a persons life that in retrospect defined that person absolutely. These experiences are necessary for their being as they are now known; without them, the person would be completely different, and would have to live a completely different life. Philosophers call these experiences contingent, however, because in some alternative world, it could have been different. These events, and the people involved in them, might never have been.
For instance, Ash might not have decided to die quite so young.
To begin; Ash was born first in his family, and upon his birth, his parents were quite proud. He was a healthy baby, who grew to become a strong and healthy young man. When his brother Roy was born, he acted just as supportively as one could hope, and he and his younger brother grew quite close. Despite their four year age difference, the two were like twins. They were inseparable, taking up the same sports (which in North dome consisted only of the most dangerous activities), and taking up the same classes in school. Ash was not happy about that last part.
He was never very good in school, unlike Roy who was intelligent and excelled. Once he and Roy graduated out of their mid-levels, both Wyo, their mother, and Daniel, their father, anticipated that the two would be applying to some Universities together, perhaps in Atlantis. But Ash put his foot down, and for the first time in his life he did something rebellious by rejecting further education and signing on for a contracted job clearing space for a new dome. Both his parents and brother were shocked; his father being a successful medical doctor, and his mother being a synthetic specialist, no one had anticipated he would walk away from the family life.
He might not have been as studious as his brother, but he was clever and willful. He gathered a lot of experience as a contracted agent, and made a number of contacts who skipped between domes. Upon returning home, though, he learned that during the construction of the dome, the party had been exposed to a number of neurotoxins, and multiple members of the group including Ash were suffering from intense cranial morphing. Most of the members died, but Ash and a few others survived horribly scarred. Ash had massive damage to the neural receptors in his brain, meaning movement was now slow and difficult. However, his father noticed that while his physical symptoms were problematic, he had an additional, beneficial symptom, of increased psychic activity. His body rapidly developed an incredible amount of psychic energy, and Ash, unable to do anything else, quickly learned to use this latent power.
Meanwhile, Roy went for three years to university, graduating with honors from programs of mechanical engineering and law, eventually becoming a mechanosynth like his mother and joining the police-force for the North dome. His parents were pleased, and Ash found himself proud of his brother. But in two years, Ash's physical condition had not gotten any better, and seeing his brother progress triggered his competitive spirit. He needed some way of fixing his body, and he saw two basic options. It seemed natural that Ash should follow his mother, and replace his damaged body-parts with either mechanic or organic parts. But Ash would once again surprise his family; he put in a formal request to become a lifetorn, and requested that his father perform the procedure and assist in the rehabilitation process.
Needless to say, his parents were outraged, and his father initially refused. However, perhaps out of brotherly understanding and having seen Ash immobile so long, Roy understood. After two unsuccessful attempts at convincing his brother to reconsider, he pleaded with their father on Ash's behalf. Knowing that his son would go through with the process regardless of whether he helped or not, Dan resolved that if his son was to do this, he would make sure it was done properly. Shortly after, Ash went into the hospital a near-cripple, and emerged reformed. He was physically better than he had been, but was no longer what anyone considered human.
Roy defended his brother's choice, and never treated him any differently. But Ash's personality was faded and gray, and it soon became an emotional strain for Roy. Roy was promoted via transfer to a government division in Aerie specializing in the arrests of criminal hackers, and only a few months after the surgery, Daniel was killed in a hospital explosion, the cause of which was never officially determined. With his father gone, and his body back, Ash got into touch with his old contacts (those that had survived, anyways), and found a number of them shocked by his choice-transformation. But one suggested a very specific, private firm, known as the Heavenly Dead. They specialized, officially, in private security and dome-clearing assistance, though Ash later discovered that some of their more wealthy clients were more professionally criminal. But the starting pay was amazing, and what was better was the entire crew consisted of lifetorn, some who like Ash had chosen the procedure for one reason or another.
So Ash joined on, and over time became well liked by the crew. He stayed in touch with his mother and brother, but was often sent to different domes, and almost never returned to North dome. Often in the Wilds, or at the headqurters in Evernight, Wyo only heard from her eldest son over transcripts, with the rare communicators. Over time, though, she became curious about Ash. His letters described his psychic abilities, and from researching she determined that he was not only rapidly developing, but quite powerful for something that had decreased mental ability. What was more, the language became subtly more human, with hints of emotion. For one reason or another, it was almost as though Ash remembered, to a degree, who he was.
So Roy continued successfully in the law, Ash continued becoming a successful soldier-for-hire, and Wyo started research into theoretical psychic theory, and how that might have had an effect of Ash's personality retention...
So this was chunked out in the last half hour after a couple of notes. It's not my best writing, but the point is there.
My original character of Roy has always been more cybernetic, so I changed him to a supporting character and made him a mechanosynth (which is possibly my favorite class of yours, with the hacker in close competition). So the character became Ash, a lifetorn merc. He wasn't too bright (starting int was 12), and the lifetorn process didn't make him any better. But he is clever (high wis), which wasn't affected by the lifetearing (?) and fuels his psychic potential. So despite his mental faculties dropping from the process, somehow his psychic abilities, and that portion of his mind, were preserved (no wis reduction from template, presence of latent memories). Presence of latent memories accounts for personality retention (bravado and glory-hound flaws). He did it to become rehabilitated, and died directly prior to/as part of the procedure (well-preserved feat).
City would have to be not too high class, but not too low class, and might lead to more physical life; North seemed appropriate.
Psychic powers not immediately in family; must come from damage, leading to lifetorn (neurotoxin? Just your basic poisons from accident in dome-creation?)
Whatcha think thus far? I'll probably retype bits just because this is a first draft, but these are the ideas so far.