The Shivering Sea is bounded to the west by Westeros, to the south by Essos, to the north by the vast frozen wilderness of ice and snow that seafarers call the White Waste, and to the east by lands and seas unknown. … Of all the queer and fabulous denizens of the Shivering Sea, however, the greatest are the ice dragons. These colossal beasts, many times larger than the dragons of Valyria, are said to be made of living ice, with eyes of pale blue crystal and vast translucent wings through which the moon and stars can be glimpsed as they wheel across the sky. Whereas common dragons (if any dragon can truly be said to be common) breathe flame, ice dragons supposedly breathe cold, a chill so terrible that it can freeze a man solid in half a heartbeat.
Sailors from half a hundred nations have glimpsed these great beasts over the centuries, so mayhaps there is some truth behind the tales. Archmaester Margate has suggested that many legends of the north–freezing mists, ice ships, Cannibal Bay, and the like–can be explained as distorted reports of ice-dragon activity. Though an amusing notion, and not without a certain elegance, this remains the purest conjecture. As ice dragons supposedly melt when slain, no actual proof of their existence has ever been found. (The World of Ice and Fire)asoiaf meme (minor characters): ice dragons (¾ legends)