Muggles' Guide to Harry Potter/Magic/Hand of Glory

Overview
The Hand of Glory, a desiccated, severed human hand, is a candle holder; the person holding it is able to see in complete darkness by its candlelight, but to anyone else, the light is invisible.

Extended Description
First seen at Borgin & Burkes, a shop in Knockturn Alley dealing in Dark objects. Harry, using Floo Powder for the first time, accidentally lands in Borgin & Burke's. As he prepares to exit, he sees Draco Malfoy and his father, Lucius Malfoy, entering the shop. Harry hides and overhears Borgin explaining the Hand of Glory and its function. It is, he says, a thief or plunderer's best friend; Lucius replies that he hopes Draco will be better than a thief or a plunderer...though unless his grades improve, that may be the best he can hope for.

Draco evidently does purchase a Hand of Glory, because Ginny sees him carrying it as he guides the Hogwarts invaders from the Room of Requirement; the hand apparently allows him to see where he is leading the Death Eaters despite the Darkness Powder he tosses after spotting the D.A. members.