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When Luna reappeared on Nightmare Night, she was no longer the small filly from before. Now an adult mare, she commanded the same respect and presence as that of her sister, Celestia. Many assumed that this was the result of her powers coming back to her naturally, but that was a lie happily perpetrated by both Celestia and the Gryphon Kingdom.

This is the story of Luna as she struggles with the remnants of Nightmare Moon and her forgotten past. The only clue she has is The Temple of the Stars where her small group of worshipers used to gather, which now lies in ruins and in the clutches of the gryphons. Some things were forgotten for a reason and the past always has a way of returning.

These two facts are well known by Gilda. Pulled along for the ride against her will, ghosts of a forgotten past have come crawling back, intent on dragging her back down to a fate worse than death. All the while, she seeks to preserve the innocence of those untouched by war and tries to protect Trixie from the harsh truth beyond Equestria's borders.

One wrong step and war shall erupt. One wrong step and the world will be plunged into a darkness that would rival Discord.

Hope is not a plan.

It has been several months since the disappearance of Twilight Sparkle..

One night, after watching her sister raise the Moon and set the heavens alight, Princess Celestia begins to bed down for the night, only to be interrupted by portal forming in her room. From out of the portal comes none other than Twilight Sparkle, garbed in strange armor.

Princess Celestia, along with Luna, Cadence, and Shining Armor, are overjoyed by the Element of Magic's return, but are justifiably curious as to where she had been and what she had been doing. And so, Twilight begins her tale. A tale of survival against impossible odds. A tale of a people fighting for the most basic right of all sentient beings. The right to exist.

The royal court of Canterlot welcomes its newest member with open forelegs: the human philosopher Voltaire, from Earth.

On Earth, Voltaire is known as the greatest enemy of tyranny in the history of literature, and a legend in his own mind.

On Equestria, the court betting pool is giving him a week before the Princess banishes him to the Moon.

Note: This story doesn't have sequels per se, but there are a couple of short follow-ups set in the present day ("Parade Coverage" and "Secret Histories"), and a prequel of sorts in "At the Inn of the Prancing Pony".

TV Tropes page.