Human to bone is a Transforming spell used by Bartemius Crouch Jr. to transfigure his father's corpse into a bone. It is unknown if it would work on a living target, though it presumably would. Harry Potter speculated that, if the Death Eaters found it, they would have used this spell, or something similar, on Alastor Moody's corpse to hide it following his death during the Battle of the Seven Potters.