Dæmon (His Dark Materials)

A dæmon /ˈdiːmən/ is a type of fictional being in the Philip Pullman fantasy trilogy His Dark Materials. Dæmons are the external physical manifestation of a person's 'inner-self' that takes the form of an animal. Dæmons have human intelligence, are capable of human speech—regardless of the form they take—and usually behave as though they are independent of their humans. Pre-pubescent children's dæmons can change form voluntarily, almost instantaneously, to become any creature, real or imaginary. During their adolescence a person's dæmon undergoes "settling", an event in which that person's dæmon permanently and involuntarily assumes the form of the animal which the person most resembles in character. Dæmons and their humans are almost always of different genders.

Although dæmons mimic the appearance and behaviour of the animals they resemble perfectly, dæmons are not true animals, and humans, other dæmons, and true animals are able to distinguish them on sight. The faculty or quality that makes this possible is not explained in the books, but it is demonstrated extensively, and is reliable enough to allow humans to distinguish a bird-shaped dæmon within a flock of birds in flight.

Dæmons frequently interact with each other in ways that mirror the behaviour of their humans, such as fighting one another when their humans are fighting, or nuzzling one another when their humans embrace, and such contact between dæmons is unremarkable.

In Lyra's world, every human or witch has a dæmon which manifests itself as an animal. It is separate from, and outside its human, despite being an integral part of that person (i.e. they are one entity in two bodies).

Humans in every universe are said to have dæmons, although in some universes they are invisible. In our universe, the books suggest, dæmons are integrated within the person. They have a naturally occurring external physical manifestation in Lyra's universe and some others. Dæmons that are already physical, such as Lyra's dæmon Pantalaimon, remain external even when they visit universes with normally-internal dæmons, such as our own. Typically dæmons and their humans are conscious or sleep at the same time. However, the dæmons of witches and shamans—as revealed in The Amber Spyglass—can remain awake while their humans sleep, and it is implied in Northern Lights that cedarwood can have a soporific effect on dæmons that allows them to sleep even if their humans are awake.

...
Wikipedia