"Wargs and the Sight" is part of the Histories & Lore, a special feature in the Blu-ray of Season 3 of Game of Thrones. It is narrated by Isaac Hempstead-Wright as Bran Stark, who provides a description of warging and greensight.
Long ago, when the world was new, the Children of the Forest sang the song of the Earth, and the Earth listened. Magic was strong in those days and the Children could commune with all the beasts of the forests, streams and air. The greatest of them could even leave their bodies to hunt, swim and fly in the skins of animals. They were the first wargs.
Then the First Men came with fire and sword. They the weirwoods and cut down the Children. Calling on dark magic, the Children raised the sea and shattered the land bridge that the First Men had crossed into Dorne. When that failed, the Children brought down the hammer of the waters upon the Neck, flooding and transforming it into the bog it is today. After peace came, the two races shared the land and the Children's gods for thousands of years.
Now comes the good part: nobody knows how or why, but the magic of the Children began to emerge in men. Maybe one child in a thousand would be born a warg fewer still would be born with the Sight. Old Nan would not speak of it and Maester Luwin never believed in it, but with with it the Children could know of events far away and even those still to come. Some say the Sight was the Children's most powerful and most terrible secret, and helped turn the tide during the Long Night.
Magic has since fled the world. Among the smallfolk, any child suspected of being a warg is left out to die. Beyond the Wall though, a careless hunter might still find his prey has claws and teeth. A man's mind to guide them, for the wildlings have a different idea of monsters.
But even wildlings keep their distance from a warg because (and here Old Nan would lean in close and whisper) how can you tell if the man is wearing the beast or the beast is wearing the man? Now Old Nan has no more tales and Maester Luwin will never scoff again. Bran says that this is fine, he doesn't like scary stories anymore, he is in one...
- Wars of the First Men and the Children of the Forest
- Long Night
- Andal Invasion