This story takes place during the Season Five finale, "The Cutie Re-Mark". As such, there are spoilers ahead.

Starlight Glimmer's plan is working. All she has to do is upset Rainbow Dash's rainboom-creating race in the past, and Twilight Sparkle's connection with her friends will be severed. And she's done it. Repeatedly. Sure, Twilight can go back in time to try and stop her, but Starlight will always be brought back as well. No matter what Twilight tries, no matter how many times she returns, she can't stop Starlight. They're evenly-matched, and it's much easier to disrupt events than it is to preserve them.

That means Starlight wins, right?

This is a fic based on the Time Loop Files, the format of which was first codified by Innortal on fanfiction.net.
Here's a brief guide.
The basic idea is, one character (the Anchor, usually the main character of a fictional setting) is looping back to the very first moments of their parent series every time either they die or some kind of time limit expires. They of course end up monumentally stir crazy given enough time.
Eventually others start to loop as well.
The reset is not always perfect. Sometimes a loop's history will be different to the "prime" loop, or canonical plot.
"Crossover" or "Fusion" loops also occur, randomly. These can involve the home loopers having a guest, or the anchor for one universe spending time in another, or replacements of one character by another.
Vacation Loops are where the Anchor (or others) decide/s "buck it" and lets off steam by doing whatever comes to mind. There's little or no attempt to maintain the original timeline.

In addition, and particularly more recently, it should be known that this story has a collaborative element to it - people may submit loop ideas or loops, ideally at the Spacebattles thread (a link to the current version of which is on the Trope page), and they may become included.

There's two page image options, thanks to Filraen - the current page image has been edited by the original creator from this work of theirs.. The other one is here:
http://hourglass-vectors.deviantart.com/art/MLP-Loops-466030169

Trolls and dragons stalk the plain
Seek for mischief they may wreak
Hush now child, they seek in vain
We are gentle, but not weak

When the night seems cold and frightening
And you know not what to do
They will be there, fast as lightning
So no harm can come to you

Do not dread the sun descending
Know that they are always near
And their vigil never ending
And they face the things we fear

For they are our good protectors
They are strong, and kind, and brave
While the Lance does still protect us
Little children can sleep safe

- Crystal Empire nursery rhyme, author unknown

After a thousand years of absence, the Crystal Empire has been freed from Sombra's curse and returned to the world. The crystal ponies can finally live free from fear and slavery, but their once mighty nation has dwindled to a mere shadow of its former glory. Still, their tribe was never known for a lack of tenacity, and with their chains broken at long last, the crystal ponies are willing to face any challenges the world might throw at them.

I these difficult times, the young crystal pony Ruby Chip has risen to knighthood, and proven herself to be worthy of joining the legendary Order of the Crystal Lance. It seems like she has achieved everything she ever dreamed of, but then she starts being plagued by dark and frightening visions from the Empire's troubled past.
To make matters worse, Ruby fears that the Order might come into conflict with the Empire's new ruler. As a former officer of Equestria's military, Prince Shining Armor is not very fond of the way the Empire's armies are run and organized, and sees them in dire need of modernization. It remains to be seen if the traditional warrior caste of the Empire still has a place in the military force he seeks to create.

Very soon, Ruby and her brothers and sisters in arms will have to prove that they are more than a misplaced remnant of a long gone era, and show that the knights of the Empire can still fulfill their sworn duty as champions and protectors.

However, whether or not Ruby herself will be ready to be the pony others need her to be, that is another question altogether.

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?

The sirens are defeated and Sunset Shimmer has restored her magic. All's well and good, right?

Of course not. What begins with Sunset's friends wanting to have a very important talk with her will escalate until the fate of at least one world hangs in the balance.

Rated Teen for cosmic calamities, trace amounts of waifu theft, and a bit more skin than Hasbro is likely to show. Cover by iisaw.

The Story Shuffle short stories "Aftershock" and "Rock On" take place in the same continuity as this story. The background details of "Fish Out of Water" apply, but the story itself does not.

This story is a sequel to Oversaturation

Even in a world that just amended the laws of physics, not everything is going to be some grand world-shaking adventure. Sometimes, it's going to be silly, or at least short. These are those stories.

Canonicity is dubious at best.

Want to see your ideas here? Put them in the fiction thread in the group!

Image courtesy of Masterweaver.