Vampire bites

If a mortal is bitten by a vampire, and their blood falls upon the ground, and they survive, the wound will always give a sharp pain in the presence of vampires, no matter how well-hidden they may be. For this reason, it is the law of the vampires only to bite once the victim is dead. However, the taste of fresh-bitten live blood is intoxicating to vampires beyond all else, and so the law is frequently broken.