Black cats were commonly thought to be familiars of witches.
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Familiars are animal spirits that come from the devil and are given to witches or sorcerers as a gift. Familiars are universally known, described in several different cultures around the world. It helps the witch by assisting with the casting spells, performing magical quests, or causing a human sickness and death. It only obeys the one witch or sorcerer and will not listen to anybody else. The witch will feed the familiars with blood through her fingers, thumb, or breast. The markings on the body made by the sucking familiars were known as “witches marks.” These animals were commonly cats, dogs, mice, birds, or toads.

The Eigi Einhamr was a pagan who could transform into animals.
©BloodyLexicon.com

Introduction

The Egi Einhamr is from Nordic and Icelandic lore. The names mean “not of ones skin” and was a pagan cult of were-animals. These men had the ability to shape-shift into animals and take on their complete form, characteristics, and powers, while still being able to think like a human. While being wolf or bear form, they would attack other animals and even humans. The forms were called hamr, and the empowered men themselves were called hamrammr.

The Transformation

One could turn into an Eigi Einhamr by wearing the skin of an animal. The human body would be left in a trance while the spirit would enter the animal body. Another way the transformation was accomplished was by using magic. The person would actually still be a man, but everyone that saw him would think he was an animal.