Wargs are people with the ability to see through the eyes of animals and to control their actions. On very rare occasions, it is possible to warg into other humans, although this act often has tragic consequences, as in the heart-rending case of Bran Stark and Hodor.
If a warg's human body dies when he is occupying an animal, as was the case of Orell, the wildling killed by Jon Snow in the season three episode "The Rains of Castamere," his consciousness can live on in that animal, although he will soon forget what it was to be human.
Notable wargs include the aforementioned Orell, who warged into an eagle after his death at the hands of Jon Snow; Bran Stark, who is capable of warging into both humans and animals; and the Three-Eyed Raven, who preferred the use of his eponymous three-eyed bird.
