In the castle dungeons no spell had worked against the piece of jewellery. Not that he could do anything, he held no wand and knew very little wandless magic. It was lucky that wizards did not need a wand to transfigure into their animagus forms or surely we would have succumbed to the cold by now. Fiendfyre had kept him alive in the glacial dungeons below the manor for this long. It was also in his favour that although regular fiendfyre could not be contained or controlled, his own brand was able to be perfectly manipulated however he pleased. 