Ring of Invisibility

Though no one knows for sure how many of these rings were made, the original maker, one Carl Swift, was a man who needed to get to places he shouldn't be.  He wasn't a thief, but a mage on a mission, trying to sneak into noble women's bedrooms.  He researched the ability to be unseen and had to look long and hard for the right ingredients to make it possible.  After he got too old to pursue his "hobby" he began to sell the rings discretely.  And when he was on his death bed he gave the ring recipe to his favorite apprentice.  Now these rings are everywhere, but still guarded and very expensive.  The ring allows a person to be unseen, but not unheard, for a period of ten minutes per day.  After twenty four hours the ability returns.  Foot prints are still left, voices can still be heard, and things touched by the person still move, so a person wearing the ring can be "seen" if not careful.