There is this neat post on Tumblr from twstpasta. And was a fun au headcanon how Mc or the NRC's s/o was destined to become a great villain, and how the boys felt about it? And I wanted to do my own spin on it with a bit of a crossover. Have you ever watched or read Madoka Magica?
Let's say the Mc/Reader came from the Madoka Magica universe, and she is one of the longest-lasting magical girls, she knows the dark secret and destiny of the magical girl and the consequence of kyubey's contract. Know where she is in twisted wonderland, with no witch to slay and the frequent use of magic to face overblot. Her soul gem is nearly dark, her time is running out. And it didn't help when Crowley proudly announced that she would be destined to be a great villain, this added a great dread on her heart. Crowley none the wiser of what those words really meant for Y/n. Soon the rumor reached the boy's ears. How would they react and watched it all unfold?
♥Riddle Roseheart ♥
*When Riddle heard this he was uncertain how to feel. they were sweet and kind and could never hurt anyone. So he decided to keep a close eye on them.
*Till one day he finally asked her if she was planning to be a villain all along. With a sigh, Y/n explained what her fate really was. From the contract to the soul gem and the witches she slew. And how she will inevitably become a witch herself, to one day being destroyed by another magical girl.
"So why would you make a wish with that awful creature?" Riddle gasped.
"I didn't really have the luxury of being able to think about it. I was just so desperate at the time," Y/n frowned.
"What is your soul gem like know?" Riddle asked in a worried tone.
*Y/n's soul gem was nearly black, and Y/n's sadness wasn't doing her any favors. Riddle hugged her close as he buried his face in her neck as he promised he wouldn't let her turn into a witch.
"I won't let that happen!" Riddle stated as he stood from his chair, " I'll never let you become a witch."
"Riddle, thank you for looking out for me," Y/n thanked as she kissed riddles forehead.
"I don't want to lose you," Riddle said as his eyes grew watery.
*Riddle did all he could to Keep Y/n from using her magic and keeping her spirits up. Y/n greatly appreciated his efforts and was happier. Till another overblot happened and the others weren't strong enough to stop them, so she activated her soul gem.
__They Turn__
*Riddle hugged Y/n's lifeless body close to him as tears ran down his face. After the fight, Riddle watched in horror as Y/n writhed in pain as her soul gem shattered and a horrifying witch appeared.
*The other students watched in horror as the creature started to destroy the school and the dorms. Luckily Crowley found a way to Y/n's world and out stepped another magical girl.
*The battle was fierce and terrifying, but the magical girl was able to destroy the outer shell of the witch.
*Riddle gasped in horror as a small humanoid figure crawled slowly towards him. It reached out its hand as it cried out, but with a swing of the sword, Y/n was defeated.
"Look's like you finally kicked the bucket," The cocky magical girl chucked as she grabbed the grief seed.
"Hold It!" Riddle growled as tears ran down his cheeks, " That was her's. this is her soul gem!"
"This is no longer a soul gem. It's a grief seed, it's a reward for saving the others from her curse," kyubey's said simply as the magical girl walked off.
*Riddle cried over the body as kyubey simply walked away.
"This isn't fair. There has to be a law against this," Riddle sobbed.
🍀Trey clover🍀
*Trey was surprised to hear this, he always perceived you as a pretty harmless person. Whenever he did see them use their power, they did so sparingly and always for good.
* Were you hiding something from him? Was it something he should be concerned about?
*Trey would pull you aside to ask if they planned to become a villain at some point. But his answer he really got terrified him.
*She told him how she wished to save her life, how kyubey changed her, how she will become a witch and is fated to die at the hands of another magical girl.
"Y-you're joking, right? This can't true," Trey said as he tried to smile it off.
"I'm afraid not," Y/n frowned as she revealed her nearly black soul gem.
*All Trey could do at that moment was to hug Y/n close and promise her he would try to help her delay the inevitable.
*Sadly when Crowley opened the mirror to her world a monstrous witch emerged and proceeded to wreak havoc on the school. The magic from the students wasn't enough, so she activated her soul gem.
__They Turned__
*Trey could only stare in horror at the knew witch monster that was once Y/n. 'why did this have to happen so soon,' he cried to himself.
*The old witch was defeated. But Y/n's witch was taken down by another magical girl from the mirror. As he looked down he spotted a weird white create with vacant eyes.
"w-who are- no what are you?" Trey asked sadly.
"I am kyubey, I'm just here to make sure that the witch being taken cared of. It's about time Y/n became a witch, she was taking a long time to become one," kyubey said simply.
"Y-your kyubey, Why would you... Why would you do something like this?!" Trey shouted in sadness and anger.
"I just want to turn girls into magical girls, then one day great witches for other magical girls to take down. Don't worry about Y/n's death, she was a necessary sacrifice for the greater good," kyubey said simply.
*Trey could just stare at Y/n's body in despair, know all he has of her are his memories.
"I will make you pay, Incubator," Trey growled lowly.
💠Cater diamond💠
"You a great villain, no way. You don't have the heart for that," Cater laughed.
*Cater doesn't take the rumor seriously, and kind of just continued with their relationship.
*And even though Y/n appreciated Cater's carefree attitude towards these rumors, she could not help but feel the worry and dispair creep up on her. not really sure if Cater would believe her about her destiny.
*Sadly when Crowley opened the mirror to her world a monstrous witch emerged and proceeded to wreak havoc on the school. The magic from the students wasn't enough, so she activated her soul gem.
__They Turn__
*Cater called out to Y/n looking for her after the battle with the witch. But when he found, he quickly ran over to her fallen form as she hugged close to him as she cried in pain.
*Cater tried to comfort her to the best of his abilities, only to watch dark smoke emerge from her as it started to take the form of something big. As it tried to take the form, he could hear Y/n's tormented screams echo from it.
*Suddenly another magical girl appears and takes down the witch.
"Y/n look everything is alright now," Cater smiled.
*But when he looked down, it finally registers how cold her body has become. Till it finally hit him, she was dead.
*Dispair quickly washed over him as he hugged Y/n close.
♠Deuce spades♠
*When Deuce heard the Rumer he was unsure how to feel about it. Y/n was such a kind person, why would they turn evil all of a sudden.
*So like Trey he would ask them if they had planned to become evil at some point, and why.
*Y/n explains how she will become this terrible being and how she would be defeated by a magical girl. All because of a dangerous contract she made when she was younger.
"no, NO. I won't let that happen! And if that kyubey thing shows up, I'll pummel them to the ground," Deuce vowed.
*Y/n didn't have the heart to tell him that there was nothing he could do to save you. So she just smiled and hugged her lover and best friend close.
__They Turn__
*Deuce was hunched over Y/n's fallen form as tears of sadness and frustration rolled down his cheeks. As he was forced to watch the other magical girl destroy Y/n forever.
*As he slowly watched the girl return to her world, he noticed a white creature staring at Y/n's body. He knew that was kyubey, the cause of all of this.
*Deuce growled as kyubey tried to reason with him for why her death was necessary. but that didn't help quell Deuces anger as he grabbed kyubey by the ear.
"You have no idea how much difficulty we go through trying to understand your human values. Presently there are six billion, eight hundred million of you, and you're increasing in number by a hundred every four minutes! What's the huge fuss over the death of each and every single creature?"
Sorry, Ace Trappola stans, I couldn't think of anything but I could imagine that he would not be swad like Cater, but is angry and devastated like Deuce when His lover dies.