Blood Quill

"That's right. Because you know, deep down... you deserved to be punished. Don't you, Mr. Potter ? Go on."

A blood quill is a Dark magical object of torture that is a type of quillthat does not require ink, as it writes with the blood of the person using it. What the user writes will be carved onto the back of his or her hand, and the blood from the words sliced into the hand will be magically siphoned and be used as ink on the parchment. The wound on the back of the hand will then heal, slightly redder than before, and then open up when the user writes again. Continuous use of it will eventually scar the back of the hand. The quill is black, long, thin, and extremely sharp.

"He let out a gasp of pain. The words had appeared on the parchment in what appeared to be shining red ink. At the same time, the words had appeared on the back of Harry's right hand, cut into his skin as though traced there by a scalpel--yet even as he stared at the shining cut, the skin healed over again, leaving the place where it had been slightly redder than before but quite smooth...He looked back at the parchment, placed the quill upon it once more, wrote I must not tell lies, and felt the searing pain on the back of his hand for a second time; once again, the words had been cut into his skin, once again they healed over seconds later. And on it went. Again and again Harry wrote the words on the parchment in what he soon came to realise was not ink, but his own blood. And again and again the words were cut into the back of his hand, healed, and then reappeared the next time he set quill to parchment"