The Long Night

The Long Night is the name given to the longest winter that ever happened in Westeros. In this time period, the Others made their first great attack against Men, "riding their dead horses and packs of pile spiders as big as hounds". Azor Ahai was the legendary hero who sought out the Childen of The Forest and joined forces with them and defeated the white walkers with his sword Lightbringer. They pushed them back to the lands that are now named "The Lands of Always Winter", Beyond the Wall.