A blood pact is a type of magically binding agreement between two parties who share their blood. It could be made by the parties cutting their hands with their wands and interlacing them and making the desired oath. Upon doing this, two glowing drops of blood would raise from their palms and mingle into one.A pact the two of them made, swearing they would not fight one another. A pact that looks as though it will have dire consequences if broken. Similar to the Unbreakable Vow, it can be presumed as J.K.R. hasn’t revealed what would happen if we break it.