( Bear with me on the Eri thing I'm doing my own thing , assuming they look so much alike )

Name: Glimmer Shoshi

Age: 16

Gender: female

Quirk: illusion

Quirk description: can disappear in a cloud of smoke , and make smoke screens and she can make people see illusions and see their worst nightmares and best dreams , she can make fake clones of herself though smoke and mirrors , hypotize people

Quirk Drawback : her eyes start to hurt and she gets very very tired , she also starts to get blurry vision
Looks:

Figure :

Fun fact: No body has ever seen her eyes, not even Bakugo or Kirishima has , her eyes are amythest purple

Hero name: Mysteria

Personality:
Glimmer assumes a very theatrical personality and speaks dramatically in the third person, posing and setting off fireworks to complete the show. Izuku's positive, helpful, and humble attitude is contrasted by Glimmer's over-the-top boasting and arrogant nature. Glimmer claims to have saved Hiroshima from an attack by an ursa major. However, when confronted by an ursa minor, she admits that her tale was fabricated and that even the ursa minor was an opponent far too powerful for her to contain. It's at this point where Glimmer drops her "Great and Powerful" persona. Despite this brief display of honesty and fear, her frequent showboating alienates the other people she develops her character through out the show , she keeps her theatrical personality but she is more honest kind and humble , she is motherly , because of her behavior towards Eri ( who says that she reminds her of her mother), so her and Glimmer get along very well

Hero costume:

Crush: Izuku or  Shoto Todoroki

Or

Bestfriend: Bakugo or Kirishima

Speaking voice:

Singing voice:

Backstory:
She was once evil, the youngest member of the leauge of villains before All might changed her up , she used to be the owner of the alicorn amulet , while it blesses the user with a untold boost to their quirk it also corrupts the user , she was a prisoner to the amulet before the heroes convensed her to take it off herself, and then she became a student a U.A being able to enroll. Her parents had lost her and there were no traces of them anywhere but All might became her saving grace he let her live with him until they could find her parents.