The return of the elements

Picture a situation such as this: A lone mother holds her child close. Outside the sun is setting and the monsters of the night are waking up. She knows they can't defend themselves should one find them, but doesn't wish her son to be worried. So she tells him the following story in a hushed whisper and a veil of hope.
The world wasn't always like these. There was a time when monsters were only in your nightmares and even there you were protected by a powerful and wise princess. During this time there was always enough food and everyone was your friend, beds were warm and the water was pure. When the war came the zebra kidnapped the six heroes of this era and their powerful artifacts.
But their trap is weakening, they will be free soon.
When they come back, they'll restore Canterlot to the beautiful city it once was and everyone will have a home with a door that locks, windows that close, warm beds and full pantries.
Then they will cure Equestria of the blight. The plants will no longer be poisonous and the water will no longer burn. You'll be able to play in the moonlight and swim in the rivers. When this day comes you'll be safe again.

Summary

This story details how the elements of harmony and their wielders will return and purge the blight, restoring the world to what it once was.

Historical Basis

The first night of the war the six elements of harmony were stolen from the tree, and the six element wielders disappeared. No one knows what happened but it is believed the Zebra did so somehow, as they were later seen using the missing elements.

Spread

Every mother looking to comfort their child knows this story. It is one that few believe but gives everyone hope this isn't how the world ends.

Variations & Mutation

How they will return often varies. The most common belief is they will arrive in Canterlot from somewhere else and restore the city then the empire. Some say they will come from the coast having escaped the zebra lands, some from the dragons in the south, and some believe their half-zebra children or grandchildren will return instead of them.

Cultural Reception

This is a future hoped for by nearly everyone, except for the worshipers. They see this as a cruel joke and the hope of the weak.

In Literature

The story is largely passed word of mouth. Some have written it down but without a proper way to mass produce books of any kind these aren't common.