You were killed. However, your body returns to life with two resident souls yours and that of an ancient, alien being. The other spirit awakened for a purpose, one that it keeps secret from your mind. There are occasional fights for control of your body.
Rebellion: As an adolescent you joined a rebellion against the local ruler, if successful you are outlawed, if it failed you escape, with only friends and family knowing your involvement. (Work with your DM to detirmine the details)
In adult life you gain a rival who seeks to undo your character, they will attempt to hinder your efforts until they get what they want. (work with your DM to determine details)