Twilight and her five friends are transported during a botched spell, across dimensions to... Ponyville, Equestria? But not the same one that they knew. Sitting on a bench is Harpsy and Babar. The Doctoress avoids apples from an aspiring Applebuck. And in a library across town, six stallions join their forces as they try to decipher the appearance of filly look-alikes of themselves around Ponyville!

"Suppose I killed them all?"

Princess Celestia had been going to spend the evening in a royal mope, but Pinkie Pie has other plans for the night, plans which involve piercing the walls of time and space with her most ambitious birthday greeting yet.

Now with a Spanish translation by Spaniard Kiwi!

SF (canon species only; no humans) Ponies were magically and genetically engineered to be the perfect servitor race. They are powerful, adaptable, intelligent and completely under the control of their creators. A laboratory accident frees one such pony from her mental chains, but how can one mare save herself and the rest of her kind if she doesn't even know she's a slave?
This is not the Equestria you know and these are not your little ponies... not yet, anyway.

Tags: Adventure, Diamond Dogs, Gryphons, NO HUMANS (did I mention that already?)
Other tags: historical, mind control, Clarke's 3rd Law, excessive use of high energy physics, before they were famous.
Detailed review by PaulAsaran.
Cover art by endrome , used with permission.
Russian translation (partial -- 'unofficially' completed in the comments)
A Soot-Covered World, book 1.

It occurred one peaceful night. Half of Equestria awoke to the sound like a double-shot thunderclap. A percussion heard in the skies and rattling windows from Apploosa, to Canterlot, to Ponyville. Nopony knew what it was or what it heralded for the world as it drew a line across the nation.

For Twilight Sparkle, this isolated incident might have faded from memory after a time, if not for the strange rumors of a creature sitting on the hill on the outskirts of town.

These are her thoughts given written form. These are Sparkle's Notes.

Report EVERYTHING to the Princess.

Early one morning, Twilight Sparkle gets up to make some tea.

Sometimes, a cup of tea is just a cup of tea. This is not one of those times.

To Twilight Sparkle and Princess Celestia, it is a simple surprise visit to Canterlot. To the ponies of the Equestrian Civil Service, it is twenty-four hours of chaos, politics, weaponized dessert, politics, underhooved manipulation of media, politics, and things batrachian and tentacular. Who said bureaucracy isn't exciting?

Humans... humans are such a bizarre race. Capable of the greatest benevolence and the worst atrocities. And yet, they're so very predictable. For you see, while societies may die, and nations may crumble, one thing will remain constant: the desire to survive.

I should know. I was there when everything fell.

Persuaded by Pinkie Pie to loosen up, Twilight Sparkle uncharacteristically deviates from her routine and finds a street that does not exist on any map, a street that should not be there. Down this road is both a threat, and an answer, one that may help us all reconcile the troubling inconsistencies between Season One, and all subsequent seasons of MLP:FIM.

♥ As Featured On Equestria Daily!

Luna discovers something hidden from Celestia for twenty years, now, with emotions running high, she enlists the help of the Mane 6... but what seemed to be a single mystery, soon reveals a darker and much more complicated plot that will soon decide the fate of Equestria.

Check out the Empty Room TV Tropes Page (Warning: Spoilers!)

Revised chapters edits and proofing (with many thanks) by: lammy, Trevor, Nick Nack, Fifth Alicorn