A Human Servant functions similarly to a witch's familiar in that when the servant is nearby, the vampire's abilities are stronger. Most or all master vampires appear to be able to create a "human servant." By marking a human with four successive "marks", the vampire makes the human into a human servant. A vampire can only have one human servant at one time, and cannot remove a mark once given. Most vampires seem to be able to exercise some control over their servants, but a necromancer servant, such as Anita Blake, has complete free will. The death of either the servant or the vampire may injure or kill the other member of the relationship.