Where do nightmares come from? The answer lies with the reclusive princess Luna, and one foal will find out when they wander away from a field trip.

Over a thousand years ago, Princess Luna created the Night Mares. They were a small but elite group of ponies, born with bat wings and strange abilities. It was their job to gallop across Equestria every night and deliver dreams to sleepers in their beds. But when Luna began to turn away from her duties, the Night Mares were corrupted. They began delivering bad dreams to all, and ponies were afraid to sleep at night for fear of the terrors that awaited.

Equestria lived in fear of its own dreams- that is, until Princess Celestia stepped in.