Inspired by:
All for None by Luketwo.
Larceny by OneSmallOof.
Black Heart by GoldenGecko.
Repeating/Rephrasing/Rewriting History by Osiria_Rosebud.
Incident Zero by YaBoyGuzma.
Midoriya Izuku was having a crappy day. He was reminded yet again that he was a quirkless freak that didn't belong in society. Hell, he even got suicide-baited by his former childhood best friend turned bully Bakugo Katsuki, telling him to take a swan dive off a roof and hope for a quirk in the next life. It was all too much for the poor lad, so he walked sullenly home, taking a path that went underneath a bridge.
He was immediately alerted when he heard a manhole cover flung open behind him. Turning around, Midoriya saw a large sludge-like being before him. It smelled putrid and had both eyes and a wide grin, showing many pristine white teeth.
"Perfect, a medium-sized invisibility cloak for me to hide in!" the being whooped before rushing over and surrounding the young green-haired man with itself. It blocked off his mouth and nostrils, not allowing him to scream for help and, most importantly, breathe. He felt as the sludge rushed into his mouth, tasting like puke and a pile of shit, drowning him slowly as he fought to remove the sludge, to no avail. "I was so worried that he would find me before I could hide, but thanks to you I don't have to! You're my hero," the villain thanked in a voice that purposely betrayed the scenario they were in.
Midoriya kept clawing at the sludge, trying to breathe, trying to stay alive. His eyes were tearing up at the thought of leaving his mother all alone by herself, never knowing what happened to her baby boy. In an act of desperation, in an act of trying to survive, Izuku clawed at the eyes of the villain, it seemingly being the few things that were corporeal on the sludge.
When he clawed at the eye, he felt an empty part of him practically sing and beg to be filled, begging him to pull from the villain.
So he did.
It felt like pulling a string from the villain and into him, if that made any sense at all. He felt the empty part of him be filled as, at the same, nearly instantaneously after the sludge retracted from Midoriya's body, allowing him to breathe and cough up the sludge. He watched as the sludge turned back into a large stocky man, who was confused that he was back to normal.
"What the hell did you do to me?!" the villain shouted as he kept trying to transform to no success.
Midoriya grabbed his backpack and ran from the scene, leaving the man to his fate as he rushed to safety. He navigated his surroundings expertly, knowing the area quite well due to avoiding Kacchan's cronies from bullying him. He easily outran the villain due to his strong legs, stopping ten minutes later and resting on a wall, trying to breathe from being slightly out of breath.
"What the hell just happened?!" he asked aloud to himself. "Why did that sludge villain turn back to normal? Why do I feel different?" He slowed his breathing as he focused within himself, trying to find that "string" that was in the (previously) empty part of him. Midoriya found it easily enough after five minutes and tugged on it, feeling his body becoming weird. He opened his eyes and found himself a puddle of putrid green sludge on the ground, his uniform drenched and sitting atop of him. "Huh?!"
He quickly stopped pulling on the string and turned back into his normal self, sans clothes. "I have a quirk? Oh my god! I have a quirk!" he yelled to himself, completely enthused with his success, before getting quickly embarrassed that his twig and berries were exposed to the air. He quickly dressed himself as he thought aloud to himself, "But what are the odds that I have the same quirk as that sludge villain?"
Midoriya thought to himself and then came to a conclusion:
"The odds of having the exact same quirk as someone else is impossible, as each quirk, while they can be similar, is unique," he mumbled, putting a hand to his chin as he rapid fired his thinking. "Having the exact same quirk as the man who attacked after ten or so years of being quirkless is nigh impossible, meaning I don't just have a quirk similar to that sludge villain…I have his quirk. This is compounded by the fact that the villain couldn't turn back into his sludge form…"
His face paled in color at the ramifications.
"I have the ability to take quirks? Wait wait wait! That would change everything scientists know about quirks! If quirks can be stolen, why hasn't it surfaced beforehand in some way or another?" he questioned, receiving no answer. "Calm down, Izuku," he told himself, breathing erratically in contrast of what he wanted. "Maybe this is a fluke? Yeah, a fluke!" he assured himself. "I don't have the power to take quirks, no one has that power! I just happened to get the same quirk as that villain at the same time he lost the ability to use his quirk! That totally happens…right?"
He held up his left arm and pulled on the new string inside of him, seeing his arm turn into the smelly putrid green sludge up to his elbow. He turned it off, fascinated by his new and startling abilities.
"I have to test this out, for science!"
He made his way home and shut himself in his room as Izuku made a new notebook that day, titled "History Notes" to throw off any suspecting person who may or may not be coming after him.
Call him paranoid, but when All Might comes knocking on his door asking about what happened to that guy's quirk he wasn't going to go down without a backup plan.
Either way he decided to test the quirk he had "borrowed" (it was less guilt-trippy to call it that than stealing) by taking off all his clothes (making sure the door to his room was locked) and activating the quirk in various parts of his body. He first started in the hands, which worked well enough, it becoming goopy and sludge-like. He turned it back to normal to write it down. He did this to his legs, his torso, his head, finding that he had good enough control of the body parts.
Eventually he managed to make a detailed analysis of his new quirk:
Sludge (Transformation-type): Allows the user to turn parts of their body into dark green sludge that's smelly. The user becomes practically invulnerable to blunt and sharp objects to any part of their sludge body, however the eyes and mouth are weak point if one transforms completely.
Theory #1: Falling from any height would probably be nonfatal if in sludge form (untested, not about to take a swan dive off a roof, thanks for the idea though, Kacchan).
Theory #2: Getting hurt doesn't work except on the eyes and mouth (tested through stabbing the blunt end of a pencil onto myself).
Theory #3: Finer control of the sludge will allow one to make weapons (tested, though it became a failure due to instability).
Theory #4: Suffocating another person by filling their lungs with sludge is possible (tested on myself before I "borrowed" the quirk).
He tapped the eraser head of his pencil to his lips, trying to think up of any more things to add to the description/theories when he heard his mother come in through the front door, making him close his notebook and greet her.
In an underground bunker, far from the light of the sun, was a deformed man breathing heavily, struggling for breath as he breathed through the ventilator. He was alone, isolated from others. He thought that he'd spend the day listening to old reruns of channels when the feed cut off and he heard three short beeps, alerting the deformed man that his doctor was paging him.
"Doctor Garaki, what is it?" he asked with a powerful voice that betrayed his horrible condition. "I was busy listening to a cartoon from the good ol' days."
"Master, a villain was found by your nemesis to have lost their ability to access their quirk," the bald doctor told him. "Eraserhead wasn't on the scene to erase the quirk, and the quirk was a transformation-type, a sludge-like meta ability."
"Hmm, the ramifications of this is astounding, but we need more information before we can better assess the situation. Thank you for telling me, Garaki, but I'm ending the call," the deformed man told his doctor. He waited a second before using his remote to dial for an underling he had, "Shigaraki, I have a job for you."
"Yes, Sensei?" came the faithful voice of his protégé, Shigaraki Tomura. Sensei/Master couldn't see the young man due to not having eyes, but the last time he saw him he had baby-blue hair and severed hands covering him.
"What is the status of one of League of Villains, Toga Himiko?"
"So sweetie, how was your day?" Inko asked her son as she gathered the ingredients to make a simple spicy stir fry.
Midoriya gulped nervously as he debated whether to tell his mother what the hell happened today. "Nothing special," he lied, not wanting to alarm and, possibly, alienate her. Despite her being his mother, he didn't want to lose her from his scary quirk.
In fact, as soon as he thought that a new hunger reared its ugly head, telling him to take another string, another quirk. His quirk practically sang when he looked at his mother, wanting him to steal her quirk, Minor Attraction.
He shook his head, doing his best to silence that part of him. Great, he had a hungering for quirks that weren't his own. Could this get any worse?
"That's good, dear," his mom replied, not knowing the inner turmoil going on in her son's mind. "Should we have chicken or ground pork?" she asked, turning around to look at him.
"Chicken, please," he chose, not really a fan of ground pork lettuce cups that she'd surely make if he chose it instead of chicken. He watched her hum in response as she got to work, making the stir fry and white rice.
They ate roughly thirty minutes later, and afterwards he was left to ponder in his locked room.
The power of his new quirk, the ability to take away someone else's quirk, was astounding; but what should he call it?
"Hmm…" he hummed to himself, trying to decide on a good name. "'Take Away?' No, that sounds stupid. 'Taken?' No, that one's stupid too!" he groaned, flipping himself onto his belly and shoving his head into the pillow. "Good name, good name, come on…What about 'Larceny?' Better, but not good enough. 'All for Me?'"
A light bulb went off in his mind.
"Wait, what if I change it around a bit? How about 'All for One?' That's it, I'll call it 'All for One!'" he declared, a smile on his face. "I really have to test taking quirks from other people, but wouldn't that be amoral?" he thought aloud to himself. Taking a quirk from someone, even if they were a villain, was wrong, right? He was taking a part of them, something special and unique from them if he did so. It was wrong, right?
Then why did it not feel wrong? Was his new quirk altering the state of mind he was having? Was that even possible?
Scratch that, that was possible, as he had read the other day about quirk madness, which was a serious issue that affected normal people. Was he experiencing a form of quirk madness with not feeling bad about taking from villains?
He hoped so as he went away to dreamland, ready to carpe diem (to seize the day), or rather the next one.