You were abducted by otherworldly beings (planar, fey, fiend or celestial) Moments later, you reappear, but has physically aged 1d10+10 years, has no memories of that lost time, and has not mentally aged even a minute.
A potent conjunction of the stars and planets occurs on your birthday. you are struck by a falling star which passes through your body like it was made of mist. you awaken feeling different, as if something has been awakened from within.
You become involved with criminal elements of society, taking to a life of crime and earning a notorious reputation and bounty. (work with your DM to determine details)