Prison Island Break is a reimagining of the Sonic the Hedgehog series where everyone is a convicted criminal. It features characters from a large number of continuities having to survive, work, or escape from Prison Island, run by the cruel warden Mephiles. Prison Island has many secrets that are darker than the hearts of the prisoners such as criminal overlord Vector having as much or perhaps more power than the warden, Scourge the hedgehog being used to punish particularly unruly criminals, and Dr. Ivo Robotnik conducting experiments on criminals to create an army of Mecha-Mooks.
The Alcatraz: Shadow has apparently tried to escape Prison Island and failed - and apparently he's actually gotten the furthest of any convict. He's pretty angry at Sonic for insisting that he can.
Shadow: First the ankle cuff. Then the cell. Then the locked doors. Then the fences, the jungle, the MILES AND MILES OF FUCKING OCEAN! And all the fucking way, there's the Guard Robos, the cameras, the grasses, and that mother-fucking bastardated sonuvabitch Mephiles. You think you're the first to try?
In fact, Sonic talks so much about escaping this inescapable prison, that the other cons and guards think he's kidding.
Just to elaborate on what Shadow is talking about: The "cuff" is an anklet permanently attached to both Sonic and Shadow. If either of them attempts to move beyond 30 mph, they get a debilitating shock. This is their particular anti-escape measure; each prisoner has some kind of clothing or procedure that negates their talents/powers. Cells are self-explanatory, fences are the electric variety, and the jungle presents it's own problems. Guard Robos are expendable Mecha-Mooks that can restrain and electrocute prisoners. Mephiles is the utter bastard of a Head Warden who keeps the prisoners distracted with fear of each other. He is fond of severely punishing anyone who attempts to escape, which serves as a deterrent for the rest. The ocean is the final obstacle of Prison Island. There are no convenient boats to steal and it's too far to swim or fly over. Shadow's attempt was stopped by the ocean, and he survived in the jungle for three weeks afterwards.
Anti-Villain: The protagonists are barely even designated heroes. Their goal to escape prison isn't particularly noble; all admit guilt, and most intend to commit more crimes on their escape. Their crimes include murder, rape, bank-robbery, fraud on a global scale (Tails claims to have nearly made himself the sole owner and stockholder of Sony), escaping other prisons, and what boils down to terrorism. It's the Morality Kitchen Sink. However, since the story is told mostly from their perspective, Sympathy for the Devil ensues to some degree.
Asshole Victim: Silver was sent to prison for killing someone who will later rape and kill a bus full of children.
Attempted Rape: Shadow attempts to rape Silver under the bleachers. Since an alliance has been formed between Knuckles, Sonic, Shadow, Silver, Nack, Tails, and Manic under the mutual goal of escaping the prison, Knuckles decides to stop him.
Authority Equals Asskicking: Vector is at the top of a criminal empire and he's just as dangerous if not more so as his subordinates. Justified because he had to climb his way to the top, he wouldn't be in that position if he wasn't Badass.
Department of Child Disservices: Convict Shadow Robotnik was taken away from his eccentric father-creator Gerald, but Social Services itself accidentally knocked down his sister Maria while doing so, fueling a life-long resentment towards The Man. He was then passed around a series of foster homes which had trouble coping with him due to his emotional trauma and the fact that he's the Ultimate Lifeform. He was finally passed into the care of foster parents who physically and sexually abused him, and who he eventually murdered. Different from many other abuse fanfics in that Shadow clearly avoids bringing it up and will try to change the subject if it does.
Silver: What... happened to you?
Shadow: Nobody ever came when I screamed. Nobody sympathized with me when I did what had to be done. Why should I help you, knowing there's nothing you can do for me?!
Depraved Homosexual: Knuckles is definitely one and it's not just to fulfill the Prison Rape trope. It's stated very firmly that he's in prison because he raped men.
On the flip side of the coin, Shadow sexually assaults Silver at one point, but it's clear that this is to demonstrate dominance.
Embarrassing First Name: Shadow the Hedgehog 's full name is Ursula Leslie Robotnik, which is why he insists that everybody call him Shadow, but Sonic occasionally embarrasses him with it. At one point he explains that it means "Oops, we expected a girl."
Worth pointing out that Leslie used to be a boy's name.
Embarrassing Nickname: Knuckles is nicknamed 'Fuckles' (though no one other than Shadow says that to his face) while Silver is nicknamed 'Preacher'.
Florencenightingale Effect: It is very obvious that this has happened with Shadow the Hedgehog, who is obsessed with Amy. It's not very romantic, and in fact is even a little creepy since Shadow is a serial rapist-murderer, and voices his desire to rape her specifically right to her face. She tries to rebuff him, or ignore his advances, but it seems she's quite fond of him too.
Gadgeteer Genius: Tails escaped from the medium security prison he was previously incarcerated in by rigging a radio to mess up all the electronics and then flying over the fence.
What keeps her from being a Purity Sue is her Sympathy for the Devil, a flaw which has her sympathising with the convicts whom the story actually revolves around, since she is clearly not The Protagonist, instead playing a supporting role.
Active and completely unrepentant for the most part. All of the powers/talents that make them heroes in canon are simply redirected to criminal ends. Sonic robbed a bank, nearly managed a second one, killed a cop in the process and escaped normal prisons with utter ease. Shadow killed his foster parents, then used his Chaos Control to rape and murder young women. He started killing men "just to even it out" and was only caught by complete accident on his part.
Mecha-Mooks: Along with regular wardens there's also the Guard Robos. They're not particularly smart or durable but are cheap, repairable, and replaceable.
Might as Well Not Be in Prison at All: Vector has just as much power, if not more power over Prison Island than Mephiles. He's even able to run his criminal empire from inside the prison.
Moral Event Horizon: Head Warden Mephiles is consistently portrayed as pretty awful, but the specific moment you're supposed to realise he's worse than any of the cons is when he bullies prison doctor Amy Rose into performing humiliating sexual acts for his pleasure, while taking photographs to use against her as blackmail material in the future, just in case. And then just as he's about to leave, he turns around and tells her she is the one who is a disgrace.
This is made even more horrible by Amy Rose being intended as a character of Incorruptible Pure Pureness.
Morality Kitchen Sink: Almost all the characters are morally dubious criminals, including those Sonic allies himself with. The most obvious exception is the villain.
Rape As Back Story: Shadow the Hedgehog was sexually abused at various points in his life. The reason it is not discussed in depth is because, quite simply, he doesn't want to talk about it.
Serial Killer: Shadow the Hedgehog is a Serial Killer-Rapist. His crimes had a Power/Control motive, with rape as another method of control. It is also implied that there are more victims out there.
Shadow: Eleven rapes, nineteen murders. And that's just what they caught me for.
Scourge the Hedgehog is also a Serial Killer-Rapist, but with a much more Hedonistic motive.
Stockholm Syndrome: It is clear that Shadow is obsessed with the Prison Doctor, Amy Rose, repeatedly telling her he loves her, that she is a good person, and that he will rape her for her own good. However as the fic goes on his affection becomes slightly less creepy. This is a sharp contrast to the Psychiatrist Blaze, whom he also threatens to rape, but much more savagely.
Story Breaker Power: It's stated that Silver could tear the whole prison apart with his mind if he had the opportunity. He was given an injection to take away this ability at the beginning.
Straw Misogynist: Heterosexual major character Shadow the Hedgehog hates women, loudly classing them as sub-people. This is how he justifies his violence towards them to himself. The sole exception seems to be Maria. Interestingly, his hatred for women is the sole facet of his personality that is neither justified nor explained.
Subtext suggests that Shadow doesn't really hate women (at least no more so than he dislikes just about every other living creature); he just rapes and murders them and claims that he did so because he hates them.
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it doesn't duplicate an existing trope, there are at least three examples, and the title makes sense.