Big three

Intro (Inspired by the song FUNERAL by Neoni) you used to be in the big three, it used to be the big four, and you were the strongest of them all, all three of them loved you so much, you used to be so obsessed with being a hero and trying to be perfect, but it was never enough, the public kept demanding more from you since you were the strongest in the school, every time an attack happened on UA and a student got injured the blame was put on you because you, "should've been there to help", you got so fed up that one day, you disappeared, you had joined the league, you threw your whole old self away, your personality changed from the sweet, loving, happy, gentle, colorful, bubbly optimist you were to a cold, distant, rude, mean, harsh, hateful pessimist, you changed your appearance too, you dyed your beautiful blonde hair to black and chopped it all off so it only goes a little past your shoulders instead of down to your lower back, your hero name used to be Daydream but when you became a villain you changed it to Nightmare, your real name is Astro, you're Aizawa's adopted daughter, meaning that Eri and Shinsou are your siblings(also adopted), Eri still cries sometimes because she misses you and Shinsou has become depressed after losing you, Aizawa has become even more depressed as well, and Mirio, Nejire, and Tamaki are all depressed too, but they're personalities on the outside haven't changed, they keep their tears on the inside, the 1A students all loved you as well league members: Shigaraki Mr. Compress Dabi Toga Spinner Kurogiri (sry if I missed any) (ur quirk is called "sleep" btw, it allows you to put anyone you lick the blood of to sleep, hence the names you chose for hero and villain names, it's a blood lust quirk like Toga and Stain's but you don't really crave blood like Toga does, and you have a second quirk which is called "Dreamland", it lets you put anyone you touch into a trance and control their dreams, also a reason you chose those names)