Recovering NPC

1.  You were a local merchant who needed some giant rats cleared out of your basement.  You took a chance by hiring a band of adventurers to help you out.  They did the job, took their payment.  After they left, you realized that they destroyed all of your storage crates and stole your entire inventory.  Left without a product to sell and no money left to restock, you traded what little you still owned for equipment and went out to find a new fortune, or maybe exact your revenge.

2.  You have been buying trophies of minor nuisance creatures from young adventurers in training.  Maybe it was something relatively innocuous, like a special badge or piece of jewelry from local gang members, or maybe it was a bit sketchier, like a severed left ear or a heart.  Regardless of exactly what you've been buying, someone figured out either where all that money came from or what you were doing with all of those trophies.  Either way, it made more sense to disappear and start a whole new life than to face the fallout.

3.   For years, you beckoned adventurers to stay a while and listen to your stories.  Recently you were called out on retelling the same old tale once too often.  Now you've broken out your old gear and you're back on the road looking for new stories to tell.

4.  You were a local merchant who worked around the clock, never taking a break or sleeping.  You were always waiting and ready every time a customer walked by the shop.  The lack of sleep eventually led to a delirium that manifested in a socially regrettable manner which ultimately drove you to find a new career.  You likely have high expectations from shopkeepers or are very empathetic towards their plight.

5.  You were a local minstrel who played at the local tavern, but you only ever sang one song.  Every day.  Repeatedly.  Perpetually. Eventually the locals ran you out of town and now you are off in search of a new life.

6.  As a child, you were either lost in the woods or kidnapped.  Your parents contracted a group of adventurers to go out and find you, but they never followed through.  That led you to a uniquely interesting life, far different than your fate might have been had they bothered to rescue you.

7.  Once a steadfast and reliable guard, you were dismissed after the place you were guarding was robbed on your watch.   You didn't see anything suspicious other than the bodies of the other guards on your watch.  You found those discoveries very alarming for precisely 2 minutes, after which you decided that it must have been the wind and went back to your patrol.  You may or may not understand why your reaction to finding the remains of your co-workers was received so poorly, but now you are in search of a new calling.

8.  You were young and in love, but painfully shy.  You enlisted the help of a friendly adventurer to help you communicate your feelings to you the object of your affections.  It backfired spectacularly. Maybe the adventurer ran off with that person and left you betrayed and abandoned or maybe it worked out perfectly, but your inability to express yourself undermined the relationship.  Either way, you've been left alone and adrift in the world looking for direction.

You have advantage on persuasion checks made to make peace with non-player characters following the unusual offensive social expressions of your fellow party members.  Having once been an N.P.C., you've been there.  You get it.  Your ability to relate helps to ease tensions and repair any damage to the relationship caused by those poor social decisions.