When I was younger my mother would tell me myths and stories about the White Walkers. She'd tell me tales about how thousands of years ago they swept through cities and kingdoms riding their dead horses and hunting with their frozen spears, killing anyone and everyone in their path, reanimating the dead as 'Wights' to kill the living at their command.
The White Walkers have now risen from their graves, causing havoc and destruction among Asgard; killing a majority of the human population, leaving only a few of us behind. Now it's up to us to protect ourselves.
(Written for a 9th grade short story assignment)