This story is a sequel to How Not To Use Your Royal Prerogative

  In an Equestria where the Sonic Rainboom never happened, Sunset Shimmer is the prized pupil of the Princess of the Sun. As Sunset struggles to make up for her past misdeeds and come to terms with the pony she wants to be, Celestia sends her to find the classic work The Application of Unified Harmony Magic from the Royal Canterlot Archives.
  Right after lunch, some meddling by her friends and meeting somepony with firsthoof experience of the Sunset she used to be.

Featured on Equestria Daily on August 18, 2016!
Appeared in the FimFiction Featured Box!

Cast: Sunset Shimmer, Moon Dancer, Minuette, Twilight Sparkle & Princess Celestia

Stories set in the Wavelengths Timeline in chronological order:

Origins Arc
The Alchemy of Chemistry
Bards of the Badlands
Grading on a Bell Curve
Habits of the Equestrian Phoenix
How Not To Use Your Royal Prerogative

Applications Arc
The Application of Unified Harmony Magics
Princess Celestia: A Brief History
The Cloudsdale Report

Dreamers Arc
Tactics of Snowbound Unicorns
A Study in Chaos Theory
Teahouses of Saddle Arabia
As the Raven Flies

Cover Credits
Cover Design by Amber Spark
Sunset Shimmer Vector by TigerBeetle
Pony SciTwi Vector by Osipush
Canterlot Bookshelves Vector by FavoriteArtMan
Sunset Shimmer Cutie Mark by MillennialDan

Beta Reader Credits
Ebon Quill - Worldbuilding Writer on The Manehattan Project
Quantum State - Technical Director of The Manehattan Project
The Albinocorn - Master of Sunset Shimmer Stories

Strongly Recommended Stories:
The Brightest and the Best by Pineta - The events in this story are considered to be completely canon to this timeline and explain Twilight's entrance exam to Celestia's School for Gifted Unicorns. I cannot recommend this story enough.
MLP Annual 2013 - "The Fall of Sunset Shimmer" - As above, the 8-page short comic in the beginning of the Annual is also considered to be canon, though with some major variations.

Version 3.0 Edit: Extensive grammatical and mechanics changes. Adjustment to timeline of Sunset's second mirror experience.

A young girl, having been robbed of her childhood and very life by illness finds herself given a second chance in a strange world and with an even stranger body. With a new life, family, and even a brother, she tries to cope with the bizarre world she's found herself in while also trying to embrace her role and become worthy of the gift she has been given.
Being a princess can be hard however, even if it's only an honorary title, especially when you're the twin sister of Prince Blueblood.

Warning, very slow burn.

MLP/Undertale crossover.
Not a PWNY-verse story.

Long ago, the Monsters and Humans fought a great war. The Monsters lost, and were sealed in the Underground. It would take the power of seven human souls to break the barrier that kept them imprisoned. They only had six. And so the Monsters waited and hoped, praying that another human would find their way to the Underground. Some thought the seventh soul would give their King the strength to break the barrier. Some dreamed of a human who would be their friend, and save them all...or had nightmares of one who would bring back the war.

...but nobody came.

...but somepony did.

Eons after the war, with no way to tell how much time had passed above, a tiny blue filly with wings and horn fell into the underground, calling for her Mama. None knew the poor creature's nature or origins...but her soul was powerful with magic, even more so than a human soul.

None can know what will come...of this little 'Woona'.

Cover art by Sanyo21

Sunset's friends ask her for help with a lot of things. Pretending to be Rarity's boyfriend at her cousin's wedding is a new one. It can't be that hard, right? A sharp suit, some expertly applied makeup, and a good backstory and she'll be charming the pants off of the bridesmaids in no time.

But just what is Rarity hoping to get out of this subterfuge in the first place?

Russian translation

Dr. Albert Wily...mad genius, evil scientist, brilliant roboticist, wanted criminal, would be world conqueror, loving father... Wait, what was that last part?

When Dr. Wily wakes up one morning with a tiny unicorn inexplicably clinging to his bald head, he is more than a little flummoxed. Unknown to him, this tiny creature is about to turn his entire life upside down, worm her way into his heart...and make his dreams a reality.

Can you feel the Wub tonight? Mega Man sure will.

Part of the PWNY-verse.
Edit: Now with awesome cover art by sanyo21! How does he do such awesome artwork so fast?
Edit 2: Adorable fan art sprite by SteamingBullet!
[img]http://orig14.deviantart.net/af07/f/2015/257/9/a/vinylwily_by_steamingbullet-d99jln2.png[/img]
Edit 3: New fan art commissioned by a fan!

Tony Stark had everything he wanted in his life. He had his company. He had a carefree life where he could simply enjoy himself and tinker with whatever came to mind...and he was a super hero to boot! He couldn't imagine ever being happier.

And then a rainbow-maned Pegasus foal dropped into his life, and turned it upside down.

Lucky for Tony Stark that the multiverse is much more imaginative than he is.

Part of the PWNY-verse.

Will freely mix several different Iron Man continuities based on what makes the story work best.

All he knew was his globe. He was left inside of it as punishment for his devious crimes, but that was hundreds of years ago. Still, he sits inside his spherical home, his mind slowly degrading as each day passes.

He can't even remember what he did wrong in the first place.

The scary thing is, neither can the alicorn who put him there.

Cover image by HoodwinkedTales
Story input by Enigmatic Otaku and ROBCakeran53

Trying to patrol the dreams of every pony in Equestria can be stressful. To ease her burden, Luna retools the Tantabus to turn nightmares into good dreams instead of vice versa. Aware of her mistakes from last time, she tests it out thoroughly, making sure there are no unexpected behaviors. And as far as she can tell, there are none.

Except that it's started calling her "Mom".

Faced with the prospect of possibly creating life, Luna seeks out Twilight's advice and assistance. With a little luck, they can get this all sorted out before the sun rises.

Because when her Pinkie Sense is going off and she just knows somepony's been denied the birthright which is their birthday celebration, she'll go anywhere and do anything to make it right. Even if anywhere means heading deep into a changeling hive, and anything is... well, anything!

But she'll do whatever it takes.

Birthdays are important.

Now with author Patreon and Ko-Fi pages.

In the first days of attempting to establish the foundation of a new nation's currency, a pair of rookie rulers decided to back Equestria's economy with the greatest offering they could make to the world: the promise of their own labor. And it worked -- but there was a certain problem with the way that promise had been made, and so the original currency was eventually recalled. But the sisters never got all of it. And legally, that promise is still good.

Whether Celestia likes it or not.

(A stand-alone, no prior-reading-necessary part of the Triptych Continuum, which has its own TVTropes page and FIMFiction group: new members and trope edits are welcome. )

Now with author Patreon and Ko-Fi pages.