No one knew how Equestria came to the Earth, or when it did, why the Barrier came with it. No one on either side of it could explain, and in the end, I suppose it didn't really matter.

The Equestrian landmass appeared one day, in the middle of the Atlantic, behind the great dome that would come to be called the Barrier. Though at first the dome was only large enough to cover a landmass the size of Iceland, on the inside there was a continent the size of North America; Equestria

At first, we were all just thankful that whatever transported an entire continent to Earth didn't result in mega-tsunamis covering the globe, but that thanks was short lived. While the ponies could come and go through the Barrier as they pleased, no human, and nothing of human make, could pass through. Worse of all, the Barrier was slowly expanding, assimilating the planet Earth into Equestria.

Nothing, no pony magic or human science, could stop its advance. Astronica, The Sovereign-Princess of Equestria, and figurehead for all the races on their side of the Barrier, worked tirelessly, night and day, along with the best and brightest of unicorn mages, collaborating with the greatest of human scientists, seeking someway to either bring down the Barrier, neutralize it's harmful effects on humans and the creations, or, at the very least, stop its advance.

In the end, all their efforts were for naught, the Barrier was implacable, and within a few short years, almost an eighth of the planet was assimilated.

Faced with the complete destruction of over six billion human beings, Asronica created a solution of last resort: the Conversion Potion. If a human consumed this potion, they would be transformed into a pony, and could then pass through the Barrier, safe, and unharmed. There was a price, however. Once transformed, the 'New Foal,' as they would come to be called, would undergo massive personality shifts, and lose all memories of their past lives as a human being. In essence, the human they once were would die anyway.

For almost half the human race, death of the self was preferable over death of the body, for as Conversion Bureaus were set up in their thousands across the planet, within several years three billion New Foals were born. Violence broke out between the pro-human Human Liberation Front (HLF), and the pro-conversion Ponification for Earth's Rebirth (PER). To the HLF, New Foals were seen as traitors, and natural Equestrians as invaders. To the PER, humans were stubborn, naive, and inferior, who needed to be brought into the future, one way or another. Numberless hate crimes were committed against both sides, and many senseless deaths followed in their wake.

Then there were those who chose to remain human. The governments of the world chose to end all wars, seeing fighting each other as pointless in the face of global extinction. For those who remained, they chose to face their deaths with dignity.

Then... it came.

We called it the Traveler, and its arrival changed everything.

An alien entity of massive power and unknown origins, like Equestria and the Barrier, it appeared without warning, and without explanation.

Unlike the Barrier, it brought something that the people of Earth were in short supply of.

It brought hope.

It revealed itself on Mars, and in the course of a month, it changed the atmosphere of the Red Planet drastically. It made rain. It turned a barren orb into a life bearing world.

Then, it came to Earth, hovering over the Barrier, which had covered half the globe by then, and began to pulsate with light, almost as if it was charging.

It continued this for seven days and seven nights, and eyewitnesses report that it was on the seventh night that the Traveler unleashed it's light, and the Traveler did what no human or pony, with all the science and magic in the world, could do.

It did not stop the barrier. It destroyed the barrier.

Earth and Equestria were now one world, and the myriad species that now inhabited this planet, under the direction of the Traveler, began a new Golden Age.

Civilizations destroyed by the Barrier on Earth were rebuilt, grander than ever. Great cities were built on the terraformed worlds of Mars and Venus. Mercury, the planet closest to the our star, became a garden world. Human lifespan tripled. It was a time of wonder, or miracles, of possibilities.

We stared out across the stars, and knew it was our destiny to walk among them.

However, at at the height of our Golden Age, came something far more terrible than the Barrier ever was.

The Traveler had an enemy, one that had hounded it over the years, and across the galaxy.

The Darkness.

In a single instant, the Darkness destroyed human and pony civilization as they knew it, and it was only a last ditch effort of the Traveler that anyone survived. The Darkness left, but the Traveler, which had saved mankind once before, now lay dormant.

Humankind banded together, and underneath the dormant Traveler, constructed The Last City on Earth. They were still vulnerable, however, as hostile aliens races closed in on the last of mankind. With it's last breath, however, the Traveler created the Ghosts, to seek out humankind's honored dead, and restore them to life.

They became Guardians, imbued with the Traveler's light, to protect the City when it no longer could.

From the Hunters in the wilds, to the Titans guarding the Walls of the City, to the Warlocks in the Tower, all Guardians swore an oath to use their light to protect the City.

What of Equestria though?

During the Collapse, and facing the full might of the Darkness, the Princess of Equestria used her last line of defense to safeguard her realm. For years under the tutelage of the Traveler, she had studied the Barrier and it's properties, and discovered how to recreate it partially.

It could not expand, for that she was thankful, but it would prevent anything not of Equestria from entering.

When the Darkness arrived at their gates, the Princess activated this magic, and the Second Barrier sprung to life, saving the ponies, as well as the griffons and other races, covering the original extent of Equestria at the time when it first appeared on Earth.

There was a price to be paid though, one that came at the cost of the destruction of most of their advanced technology. For the barrier still destroyed humans and all their creations, and Equestrian civilization relapsed hundreds of years.

The enormous strain of erecting the barrier also killed the Princesses after casting it, leading to the pony race separating into tribes based on their sub species.

They were alive though, and they could start again.

A millennium and a half later, it is one year since Princess Twilight defeated the evil and powerful Lord Tirek. She is still settling into her new role as Princess of Friendship, and tacking her duties as one of the four rulers of Ponykind.

Little did she know, or any Equestrian for that matter, that the Second Barrier, which had protected her home since time immemorial, was about to fall...

Author's Notes:

The MLP half takes place in an AU Season 5, and Destiny is in-between 'The Dark Below' and 'House of Wolves.' Some characters and elements from 'Equestria Girls' is here, but the movies are not canon.

Also, while the Conversion Bureau was used as a plot device in the prologue, this is not a Conversion Bureau fic.