Ponyville faced an ordinary day, but then night came, and with it a massive gateway into another world. It closes before any action can be taken, but now the Mane Six and Canterlot nobility are tasked with finding out what they can about the gateway. Who created it? Where did it lead to?

And most importantly, did anything come through?

Takes place after Season 2
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One cold autumn night, Twilight Sparkle lets in a pale and weary traveler into her home. When she accidentally discovers his dark secret, she is assaulted by him, and is left to die... When she woke up, she finds that she has been turned into a Vampire, an ancient enemy of Equestria last seen during Nightmare Moon's Rebellion. She now walks the thin line between life and death, sustained only by the blood of others.

Her friends now race against time to find a cure for this ancient curse, and stop the Vampire who infected Twilight, before he can create a new army of Vampires to conquer Equestria. Otherwise, Twilight will join the forces of evil and darkness, as the Bride for the Lord of Vampires. They have to work quickly, as every day passes, Twilight's thirst for her friends' blood increases...

It is seventy-five years after the HLF and human intelligence services defeated the pony invasion of Earth. Celestia is a prisoner of mankind, reduced to being a source of magical blood used to make ponification potion. Ponification has become the punishment for even minor crimes. Yes, humanity stands triumphant. So why are the HLF and the PER back? Is Celestia really so powerless? Does she have a plan? Or has the loss of Equestria and all that she loves simply driven her mad?

This story is a sequel to Chatoyance's Conversion Bureau story Brand New Universe: Chapter 7 - Mankind Triumphant - please read it before reading this one. When I first read Mankind Triumphant it shook me to the bone. It scared me, it kept me awake, it affected me. When she invited others to submit stories around her New Universe scenarios, I knew I could not refuse. I felt this story calling to me. Resistance was futile. So here it is. BTW I have Chatoyance's permission, for which I am very grateful indeed!
Artwork by Mythee AKA Glowball

This story is a sequel to Kind Hearts & Coronets

“My name’s Daisy Jo Martinez. I was born – or so my birth certificate says – on March 30, 2012. I’m married with two kids, my husband’s a Naval officer. I’m originally from a town just outside of DC called Winchester, Virginia – apple capital of America, yay, go me. I’m a Republican – that tends to shock a lot of people – and I’m a practicing Catholic – and that tends to shock more people than the first, and like I said, I’m married – I think people start passing out at that point. I've lived a happy, charmed life and I’m proud to be an American.

“And as you can also see, I’m a pony. Well, physically anyway."

The first main story of The All-American Girl Saga.
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Selected as "Humans Aren't Bastards" Group's Mods' Choice July 2013

One day, Fluttershy wakes up only to find herself in a changed world. Ponyville and Equestria are not how she remembers them: airships cross the sky, steam-powered machinery drives the economy and the rule of Celestia is no more. In this strange alternate world, Fluttershy reunites with her dear friends and learns of the event that changed history itself. Worse, the timid pegasus seems to have arrived just in time to witness the rapidly approaching climax of a civil war that has been raging for three hundred years...

Twilight becomes alicorn of the stars. This is sort of a problem, because Luna kind of already was alicorn of the stars. Oops!

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In an effort to keep her mind occupied, Twilight Sparkle decides to delve once again into the grand mysteries of Pinkie Pie. This time, Twilight's focus is on her claims of growing up on a rock farm: like so many things related to Pinkie Pie, the idea that somepony could grow rocks as an agricultural product makes absolutely no sense. However, the investigation eventually leads Twilight to a rather... surprising discovery.

This is the first story in The Petriculture Cycle.

Artwork by Page Turner. Now with a TV Tropes page.

This story is a sequel to Upheaval: Breaking Point

Following the events of Breaking Point, Twilight Sparkle and her friends discover that Equestria's demise may not come from an enemy invasion, but from within. The Barrier Lands and the Heartland begin the slow and uneasy process of reuniting into a single Equestria, but this long-delayed joining is already in danger at its conception.

With Celestia's power in her grasp and her agents by her side, the wheels of Black Rose's plans for Equestria's future continue to turn. However, her brazen gamble has done more than just bring down a centuries-old barrier. Ancient powers begin to stir: the remnants of a dark period in Equestria's history, the immortal inhabitants of Celestia's homeworld, and a rising tide of darkness coming ever closer.

Equestria is a land of magic and harmony, a peaceful realm ruled by immortal and benevolent monarchs. At what cost is this possible?

Following the discovery of a strange and powerful device, Twilight Sparkle is whisked away to the edges of a land she thought she knew so well. Here, surrounded by ponies whose very existences have been kept secret, she must contend with vicious enemies, hostile allies, and the truth.

Chapters 1-16 edited by KiltedKey

It is the year 2038, and the Earth is slowly being consumed by a space-borne monstrosity dubbed the Black Tide, which is using nanotechnology to remake the planet into something hideously alien.

Erin Olsen works for Project Harmonics, humanity's last-ditch effort to find a new world before the Tide can wipe them out. But when that world is found, and it turns out to be occupied, Erin will need to find the courage to face the unknown in order to save the inhabitants of both worlds.

(Many thanks to Easteu for the fantastic cover image for this story!)

Now with its own TV Tropes page

There is now a follow-up to this story: Sunflower - Side Projects
Sequel: Project Sunflower: Harmony