A blood-tie is a method of expanding and uniting families or particular clans among Night People. The main component of this tradition is the exchange of blood between two or more of the parties involved in the expansion. This ceremony is also a method of creating a formal truce between enemies.
In the series, there have been two forms of blood-tie ceremonies. Among vampires, as seen between the Carter siblings and the three Redfern sisters in Daughters of Darkness, the ritual is carried out by ingesting the blood of each person of the opposite clan or family involved, and vowing to remain kin to one another, promising protection and defense to the opposite party. In addition, as stated by Kestrel Redfern, those bound by blood-tie also share the blood-feuds of one another.
In Witchlight, a second version of the blood-tie is shown between Keller and Iliana Dominick; Iliana cuts both Keller's palm and her own, placing the two wounds together and announcing Keller as her blood-sister.
- Maeve Harman and Hunter Redfern
- Rowan, Kestrel and Jade Redfern, and Mark and Mary-Lynnette Carter
- Iliana Dominick and Raksha Keller
- Two prominent families of the Night World are tied together - the Redfern Family of Vampires and the Harman Family of Witches.
- Had Galen Drache performed a blood-tie with Iliana Dominick, three prominent Night World families would have been tied together - the Redfern Family, the Harman Family and the Drache Family.