The smoke and ash clouded his eyes, and in the sky he saw a great winged snaked 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.
It has been suggested that the winged snake seen by Bran through Summer is in fact a dragon that had lain dormant under Winterfell. The razing of the castle woke and freed it. In support of this idea are the hot springs on the grounds of Winterfell. Others suggest that the wolf was seeing a column of smoke and fire and interpreted that as a winged, fire-breathing snake.