Great winged snake
The great winged snake refers to something seen by Bran Stark through the eyes of his direwolf Summer during a wolf dream he has after the sack of Winterfell, while he and his companions are hiding in the crypt of Winterfell. At night, as Summer is exploring, he looks up,
The smoke and ash clouded his eyes, and in the sky he saw a great winged snake whose roar was a river of flame. He bared his teeth, but then the snake was gone. Behind the cliffs tall fires were eating up the stars.
There has been some debate among readers as to exactly what Bran saw in the sky. Some believe that it was simply fire and smoke in the shape of a dragon, or even the red comet, while others believe that Bran saw a real dragon in the sky.
…a great winged snake whose roar was a river of flame.
– Osha, emerging from Winterfell's crypts
We made noise enough to wake a dragon.
- The Westeros forum: Dragon sighting at Winterfell?!?