Basically you grew up in the lab.. You got experimented on with your powers... You escaped a long time ago you used your powers on everybody killing them...not the other kids that got experimented on but like the guards and stuff.. The owner of the lab, saw what you did before you left, and he said to, "what did you do" you moved to Hawkins and started a new life and your a boy by the way..you started dating Will byers! You haven't told him about anything in your past and you don't even bring it up.. One day he wasn't there, and you were using your powers, and you broke something, and he came back and saw it, and said, "what did you do" he wasn't mad but it triggered you... and you got flashbacks of your past when he said that