A Deal's a Deal(Reader x Bill Cipher)

When (Y/N) was still in the womb, her parents made a deal with Bill Cipher that if he always watched over (Y/N), they would never get in the way of his plans. But what happens when Bill discovers that there is more to (Y/N) than they seem?
This can be girl or boy reader but bill is a boy so the pronouns will be female. if you are a guy, just input male pronouns.