"A sample of the person’s blood had to be cemented into a personal item of the controller - for instance, the sisters’ kept the men’s blood in a family locket sealed with their own blood. The incantation is the trickiest part of it." Narcissa spoke as if she had just been brushing up on this story the other day. Maybe she  had  been. "The wand that casts the cantation can tap into the  Ethos Communion with just a whispered word."