Percy Jackson and Annabeth Chase have gone through a lot. They fought the Minotaur, Medusa, a Manticore, the Chimera, Kronos, and even Arachne, the Spider Queen. It was during this last fight that they recovered the Athena Parthenos, a sacred statue that would help secure the demigods' victory over Gaea and the Giants, but the unexpected happened: the floor gave away, and the pair fell all the way down to Tartarus. The first thing they noticed, was that a large mirror, that no monster would approach, not even for some tasty demigod blood. They were trapped, and the only way to save themselves, was through that mirror. What was on the other side, however, was even wilder than they ever thought possible.

(Added romance tag and made story "Teen" for planning on future chapters, and romance mostly in post-story Extras section.)

(Being a big Percy Jackson & The Olympians fan, I couldn't help but notice that Tartarus existed in Equestria, according to Twilight. This story recounts the events of Percy and Annabeth's journey into the other side of the Pit, and beyond.)

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

Discord is once again loose, but after using his randomness to find some interesting information on some strange phenomenon in another world that has to do with an island and a bunch of humiliating events, the crazy spirit of disharmony and chaos comes up with a new, sick, twisted, disturbing plan that involves capturing 20 of the most popular ponies (and three non-ponies) and forcing them to play a new game while the rest of Equestria watches in horror (or most likely secret amusement and possibly envy of not being picked themselves).

What does the rotten host Discord have in mind for our 20 unfortunate selections? Well, looks like you'll have to wait and find out! Maybe, just maybe, if Discord is feeling generous, the winner of his new "game" will get a grand prize. Everyone pick a character to root for and let's get it on!

(Special thanks to shadow0knight for creating the cover image. To see the full-sized image, go here: http://shadow0knight.deviantart.com/art/Total-Magic-Pony-Island-Title-293752756)

Somepony had stolen Twilight's crown and she traveled through a magical mirror in the Crystal Palace. Twilight, and unexpectedly Spike, travel through the mirror to a world she was not prepared for...

Mixing Equestria Girls and Harry Potter.
Cover Art by NinjaHam
Featured on FIMfiction's "Popular Stories"

There has always been a little voice in Twilight Sparkle's head, whispering dark musings to her. And until her brother's wedding, she has managed to push those bitter thoughts away and focus on the good. She forgives and forgets and holds onto hope.

But when her friends turn their backs on her and her brother cuts her from his life, Twilight finds herself alone, with only the little voice to comfort her.

And it is through anger and hate that has been repressed for so long that Twilight finds the power to rise up. Harmony and Friendship have only brought her pain and suffering. It is time for her to embrace her dark side. No longer will she worry about what others think. Twilight is going to live her life how SHE chooses: without friends, without family, without love and without harmony. She is going to cut loose, have fun, and screw what others think.

For her friends and family, it will soon become apparent that if they don't find a way to mend the damage they've done to the lavender mare...Twilight Sparkle might be lost to them forever.

Thank you to everyone that got this story as one of the Featured Stories here on the site!

The TvTropes Page can be found here: http://tvtropes.org/pmwiki/pmwiki.php/FanFic/FaithAndDoubt

Cover created by the amazing FerGarcia220

After an unknown accident Twilight Sparkle and Rainbow Dash awake to find themselves sharing the same body! Now they must struggle to hold themselves together as their world is turned upside down. How long can two ponies exist in a single mind? It’s a race against time as they search for answers before it’s too late. When all is said and done, you’ll never look at Twilight Dash the same way again.

Rainbow Blitz and his friends are having a harmless sleepover, until Bubble Berry brings out the candies. Not just normal candies, but ones that make him teleport to a new dimension! Will Blitz be able to survive in a world filled with mares, or will he die trying?

Contains: R63, Language, Terrible jokes, and more

EDIT: This is under construction, probably gonna rewrite a lot of it, so sorry for the inconvenience.

Twilight was on the road to recovery from her mental illness. She had started a new treatment, bonded with the staff, and had many friends in her ward. Now she wakes up in the center of the delusions she has been trying so hard to escape: Ponyville.

Inspired by Asylum by Daemon of Decay
Proofreaders: ArgonMatrix, The11thWonder, Gage, Breath of Plagues
Story and Plot Development Help: Daemon of Decay, AppleCrumble