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There is a reason that horcruxes are so taboo that they have been mostly forgotten.
What Voldemort never knew and few people in the wizarding world understood is that souls are eternal. Perhaps the true problem is that people don't understand the concept of eternity.
Simply put, eternity is the 'real life' synonym of infinity. If something is eternal, then it will always be that way and- this is the important part- it has always been that way. When one tears one's soul, one is changing an eternal thing, and that has shocking and huge consequences.
The truth is that changing a soul changes time. When Tom Riddle tore his soul in two, his soul was not the only thing being casually ripped apart. When Tom Riddle split his soul, he also split the universe, creating an alternate reality in which his soul was already torn in two. Both halves were still inside him in this new universe, but one half was simply there, unconnected and inaccessible to him, waiting to be put into a horcrux. The more he made, the crueler he became, until he finally stopped at seven. Of course, his soul wasn't split equally; the truth was much worse. If his soul had been split equally in seven, he would have had access to about fourteen percent of his soul; a very small soul, of course, but large enough for him to simply become a murderer, or a serial killer, instead of a megalomaniac intent on genocide.
Unfortunately, his soul was not split equally; it was split in half seven times. By the time he completed this travesty, little Tommy Riddle grew up with access to less than one percent of his soul. Instead of going into Ravenclaw, where the bright and friendly, if somewhat shy, boy was placed originally, he went to Slytherin, the house of the purebloods, where he was taught to care nothing for others, and that the ends always justify the means. Oh, yes, Tom Riddle grew up very differently the first time around.
The first difference was that he wasn't bullied. Muggles, for reasons unknown, are better than wizards at unconsciously sensing the state of a person's soul. (For example: If faced with the secret keeper of a Fidelius charm, a muggle might say, "What aren't you telling me?" or "What are you hiding from me?") Because Tom Riddle's soul was whole, the charismatic boy was well liked at school, and loved at home, where he lived with his adoptive parents and grew up as Tommy Jenson. Tom Riddle was never adopted in the worlds created when he split his soul, because the couples looking to adopt always felt like something was off about him, or wrong with him. They were right.
How, then, did happy, loved Tommy Jenson of Ravenclaw come to create a horcrux, an act that required murder? Well, the answer is quite simple and quite sad.
His parents were killed in an air raid while he was at Hogwarts. He was in his third year and had only recently turned fourteen. When he got the news, he cried, and cried for days. He cried until he couldn't cry anymore, and when he was done, he simply felt empty and cold. He didn't speak to anyone, rarely ate, and first his nights, then his days, were spent feverishly poring over necromancy books while he neglected his schoolwork. No one knew they were necromancy books, of course; he had disguised their covers. However, he eventually hit a dead end (no pun intended) in his research. He decided that, if he couldn't bring his parents back to him, he would go to them. The school nurse was able to save him, but only barely. He was very carefully watched, but it wasn't necessary… Well, not for the reasons they were thinking.
Tom Jenson's brush with death terrified him, and he instead became obsessed with avoiding it, at any cost. By the end of his third year, he was ready to look into Dark magic, having looked in vain for an answer among the more acceptable types of magic. As closely watched as he was, however, he knew that he would never be able to access Dark books. So, his new goal was to ease his watchers' minds. He changed his habits; he was neatly groomed, attended all meals, and became an outstanding student.
They might have been convinced that everything was normal, were it not for the screaming nightmares he had when he was asleep, and the emotionless mask he wore when he was awake. Eventually the nightmares stopped, but only as dark circles appeared under his eyes as evidence of his attempts to escape the nightmares by avoiding sleep altogether. He was given Dreamless Sleep potions twice a week, which was as much as they could give him without risking addiction. He loathed those potions. Desperately, he searched for a way to escape the mandatory drugging. Eventually, he found one and the circles disappeared. The staff of Hogwarts breathed sighs of relief- except for one. Albus Dumbledore seemed to be the only one who noticed the somewhat manic gleam in Tom Jenson's eyes.
He was right to be worried. Tom Jenson still wasn't sleeping, because Tom Jenson had found a Dark ritual that took away the need for sleep. The cost didn't seem high at all; the cost of not needing sleep was not being able to sleep. However, humans truly need sleep, and the ritual didn't take away many of the effects. Truly, the price the ritual demanded was his sanity.
By the end of his fourth year, he was a model student, and so the next year the teachers decided to reward him; he was made a prefect. They were so happy about their success in rehabilitating him, and he was such a charming young man, that they were often and easily persuaded to give him things that he asked for. After all, he had kept his Dark leanings a secret; they saw no reason not to give him a pass to the restricted section, to 'help him with his research.' They chuckled to themselves as they wrote a pass for the ever-curious Ravenclaw, and never even realized that they were, in fact, writing a pass for their own destruction.
And they were destroyed. Alternate universes usually cannot coexist. When an Alternate Universe is created, one of three things happens: Sometimes they are so similar that they repel each other, like magnetic poles of the same charge. In this case, they are able to exist separately (though this happens very rarely). Other times, one Universe is stronger and more stable than the other, so the less stable Universe ceases to exist. This happens regardless of whether they are similar or different. If they are similar, the weaker Universe does not survive the forceful separation, and if they are different (and therefore attracted to each other), the weaker Universe ceases to exist when they are forcefully reintegrated. Finally, if two unsteady dissimilar universes are created, they are both destroyed when they are forced back together. (Theoretically, two strong dissimilar universes could be forced back together, but they would both exist at once. This would be the sort of Universe in which everyone has an evil twin. Thankfully, that has yet to happen.)
In this case, Tom Jenson ended his universe when he created his first horcrux at sixteen, using the murder of a German pilot to split his soul. The man's death was the last part of the ritual, and when he killed the man he was horrified at what he'd done- both to the man who had simply been following orders (and might not even have been part of the raid that killed his parents), and to himself. That horror was finally able to reach through his grief, and he cried once again for his parents, and in sorrow for his actions.
He would have gone on to atone for his mistakes, and try to find a way to make up for the horrible things he'd done, but he never got the chance. Tom's universe had split with his soul. The two were very different, and came rushing back together, as is usually the case. As surprising as it seems, the world was stronger and more stable with Voldemort. Tom Jenson was destroyed. Voldemort continued on, never knowing that he was tearing the universe each time he tore his soul.
A/N: Well, that's that. Many thanks to CatrinaSL for looking this over for me- she did a wonderful job making the technical stuff more readable. There might be another chapter or two about the Tom Riddles between Tommy Jenson and Voldemort, but I'm marking it as 'complete'- don't hold your breath waiting for them. Hope you enjoyed it!
