Black Quill
A cursed quill that needs no ink because it writes in the user's own blood, carving the words into the back of their hand as they write.
Whatever the writer puts on the parchment is cut into the back of their own hand at the same time, and the blood from those cuts is siphoned up to serve as ink. The wound closes afterwards, a little redder than the skin around it, and opens again the next time the quill is used; used often enough, it leaves a permanent scar. The quill itself is black, long, thin and extremely sharp. Dolores Umbridge of the Ministry of Magic set students who displeased her to write lines with it in detention.
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