A Song of Ice and Fire Wiki

Skinchangers are people who are able to enter the minds of animals and control their actions.

Being a skinchanger makes way for changes in the personality of the human and the animal involved. In addition, a skinchanger bond is easier if the human already knows and is close with the animal, like Bran Stark and Summer. Usually skinchangers begin by entering the mind of the animal in their dreams. If an animal is killed while a skinchanger is inside its mind, it is traumatic for the skinchanger, and if a skinchanger is killed while his or her conscience is inside the animal, some of his or her conscience may remain in the animal. A warg is a term for a skinchanger who specialises in controlling dogs and wolves.

Arya Stark is believed to have some warg abilities, as her dreams often involve Nymeria, her direwolf.

Jon Snow is also an untrained warg and can enter the body of Ghost.

Bran Stark is the most skilled warg in the Stark family, and has repetitive dreams in which he enters the body of his direwolf, Summer. This began mostly after he became unconscious and crippled. Jojen Reed, a visitor from House Reed, helped him learn about his abilities.

Like everything else, it is better if the skinchanger has a master who teaches him to learn to master his abilities. A a masterless skinchanger would find it harder to control his abilities and even harder if the skinchanger refuses to accept himself as a skinchanger.

Skinchangers call their power a gift of the old gods. usually allows the skinchanger to control the animal.  But if someone is born with a strong gift, he can control many animals.

There are three rules that skinchanges should never do these are called abominations:

To eat of human meat is the 1 abomination.

To mate as wolf with wolf is the 2 abomination.

To seize the body of another man is the 3 and also the worst abomination of all.