Familiars are animal companions kept by witches. They differ from ordinary pets in that they are believed to enhance or assist with a witch's magic. Little is known about the exact nature of familiars, including whether only specific animals can be regarded as familiars, as they are mentioned only in passing in Spellbinder. Keeping familiars apparently arose from witches' close connection to nature. However, after the Burning Times, witches were banned from owning familiars. It is unclear exactly why this is; one possibility is that familiars drew too much attention to witches from humans, who persecuted them. That being said, many witches still maintain close relationships with animals, such as Thea Harman, who often uses magic to heal sick or injured animals and is interested in zoology and veterinary work.
- Medieval Christian beliefs held that familiars were actually demons or evil spirits that took the forms of animals, often a black cat or a hare. People - particularly the elderly - who lived alone with only animals as companions were therefore suspected of being witches. This is probably where the popular image of witches keeping cats came from. Other beliefs hold that familiars are more benevolent, serving as spiritual guides and protectors, such as a totem or spirit animal.
- Seeing as many of the laws of the Night World are often ignored or amended by Circle Daybreak, it's possible some Daybreaker witches have resumed keeping familiars, though this is not mentioned in the novels.