You haven’t given me any ink,” he said.
“Oh, you won’t need ink,” said Professor Umbridge with the merest suggestion of a laugh in her voice.
Harry placed the point of the quill on the paper and wrote: I must not tell lies.
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.
Harry looked around at Umbridge. She was watching him, her wide, toadlike mouth stretched in a smile.
“Yes?”
“Nothing,” said Harry quietly.

Auteur: J.K. Rowling