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

Tirek. Discord. The Changelings.

The ponies have faced all these threats, and triumphed, but things could have been handled better. Princess Celestia knows this better than most. She knows that to face threats even greater than Tirek, greater than Discord, the ponies need allies. They need friends to turn to when the chips are down and the mad gods and cruel tyrants are on the horizon

She and Princess Twilight Sparkle travel to the Griffon Kingdom to meet the Griffon King. They seek to negotiate a formal treaty, something more than a rudimentary "You stay in your yard, we'll stay in ours." If the Changelings invade, or Tirek is once more a threat, it will not only be the ponies standing against them, but the griffons as well. It's only logical, after all. The griffons and the ponies share a border. They share ideas. They share refugees and concepts and cultures. And there haven’t been any major hostilities since the Pony-Griffon War. That was almost a thousand years ago.

It is logical to enter an alliance, but politics aren’t always about logic. Sometimes they are about past crimes, mistakes, and tragedies. Sometimes, past grudges simply can't be let go.

(Rated Dark and Teen for some disturbing content, though nothing too heavy or overt)

Coverart from Pie on furAffinity

In the magical land of Equestria, two alicorn sisters raise the Sun and the Moon every day to give the world a night and day cycle, basic for the survival of life. There are also two alicorns who rule over two very core aspects of life and harmony itself. Those are Love and Friendship. While not as ancient as the two sisters, all princesses are essential to the world's balance.
This balance is also sustained by the hard-working ponies, who make the seasons change and manage the weather to fit their needs, so everypony has enough food and water, and every animal is also attended to assure that any of them are caught in the changes of seasons.

But what about the planet itself? What about Mother Nature?
This is the question that Gaia asks when she arrives to this foreign world. After so much work her son persuaded her to take a long vacation in Equestria, saying that she needed one and assuring her that he would be in charge now, and she must take a break. But what can a several billion-year old alicorn possibly do to pass her time in this land?

(SimEarth/MLP Crossover)
(Timelife of Gaia's life 'till the start of the story)

Frost Windchill is known to be a storyteller of sorts. Comfortable with telling the occasional sprite tale or legend, a child approaches him one day and asks for a real story.

And so Frost tells one- the story of his life. It's not a typical story, and there's more to it- just as there's more to the descendant of a Lunar Guard. It's a story not just of himself but the heroes he stood beside- big and small, legendary and obscure. But there's something amiss, buried lies between the lines.

After all, it's hard to kill memories when you remember everything.

(Cover done by the amazing Sw1tchbl4de. Check him out here! http://sw1tchbl4de.deviantart.com/

Larger version of cover art can be found here: http://sw1tchbl4de.deviantart.com/#/d4ovlt2)

When a Necromancer is hurled into the place between places then escapes to another world at the cost of his life it is not the end. Being a Necromancer he returns to life with ease, but is skirting the edges of consciousness, and unable to truly wake as a mysterious figure uses magic to put him on the back of a horse to carry him away into the night.

To make matters worse the phylactery he used to save his own life recreated him as a member of the dominant race with... some errors. His injuries are still present and he's now in a much smaller body with his magic drained to nothingness.

So now he's horribly injured, held captive by an unknown force, in an unfamiliar body, in an unfamiliar world and completely exhausted. He's had worse days. He just can't think of any off the top of his head. So familiar territory then, nothing to worry about.

(Thank you again Tulip for the amazing piece of artwork.)

On Hiatus due to Life. Sorry.