With gritted teeth, Tom returned to their lesson on parsel magic. The mark of his followers had always served as a leash, as well as a protective tether. Harry had wanted to follow in these footsteps. However, the young man had made it quite clear that he disapproved of the "punishment'-option. Yet the general concept, knowing where his friends were, reaching them and having them find him at all times, seemed like a good idea. It would just have to be at a more concealed spot than the wrist. Also, Harry had decided that he would not be opposed to being able to cast spells through the mark. A Protego at the right moment could save a life, after all.