Legends of Equestria is a partially published alternate continuity fanfiction set in the My Little Pony: Friendship is Magic universe. Spanning the entire history of ponydom (starting before the species even evolved) the continuity seeks to rationalize the universe and provide origin stories and explanations for many of its established features. The plot follows Princesses Celestia and Luna through all the years of their lives, through the tumultuous times of establishing the free kingdom, and the internal struggles that define who they become.It is actually merely a constituent work in a much larger universe, which will eventually include 14 stories: 2 trilogies, the quintology Legends, one independent work, and a final duology. In this universe, Equestria is merely a small country on a much larger planet. This planet is controlled entirely by one massive empire, which despite its incredible technological superiority, is unable to match the power of magic militarily.Originally started as a simple retelling of the events of the show, it has since expanded into a story told in five Acts, each covering a period of Equestria's history. As stated above, the work is only partly published, so some of these are not public as yet.
Act I: Ascending Star - covers the time leading up to the Royal Sisters' overthrow of Discord for the first time, along the way setting up the free kingdom of Equestria.
Act II: The First Equestrian Civil War - covers a roughly 500 year interval after the conclusion of Act I, wherein the two Princesses must put down a rebellion centered in the province of Ponyville and aided by the Pegasi (exiled after the events of Act I). The Act ends with the first emergence of Nightmare Moon.
Act III: The Silver Age of Equestria - covers the 1000 year interval where Nightmare Moon is imprisoned in the heavens, and features Celestia consolidating her power as sole High Princess. Unable to wield the Elements of Harmony since her connection to Luna is broken, Celestia assembles a group capable of unleashing their power, and the Act ends where the show begins.
Act IV: The Fall - covers the plot points discussed in the main series canon, from the re-emergence of Nightmare Moon to the defeat of Queen Chrysalis and the changelings.
Act V: Supernova - branches from the main canon in order to bring a full conclusion to the main conflicts of the plot, and ends four years after the events of Act IV.
Aerith and Bob: a reason is offered as to why some ponies have regular generic names while others have names indicative of their special talents. Since ponies are named at birth but don't receive cutie marks until they come of age, there is just as much chance of the name turning out completely wrong as there is of it lining up right. Since the fallout is potentially very embarrassing, some parents choose not to take the risk and use generic names instead.
Big Bad: The Emperor, leader of a highly advanced race of lizard-like creatures and also supreme ruler of a planet-wide empire, of which Equestria is "but a speck". He would prefer that Equestria function like a normal province instead of like a secluded protectorate, and eternally threatens to force Celestia to accept his technology.
Brains and Brawn: In Act I, Celestia and Luna are set up like this. The elder sister is an intellectual/magical prodigy and a Chessmaster, but she's next to useless in a physical fight, so Luna has to be the one to defend her.
Bread and Circuses: the kingdom that Celestia has built by the end of Act II comes to resemble this, by using weather control to establish a stable food supply and her cutie mark spell to nudge ponies into lives that make them happy.
Conflicting Loyalty: comes out in a big way with Princess Luna in Act II, when her and Celestia agree to split responsibility for the country between day and night after the disastrous Battle of Ponyville. Luna swore undying personal loyalty to her sister, but cannot stand idly while the freedom she fought for is destroyed by Celestia's dictatorial governance.
Doing in the Wizard : In one of the Appendices, the author points out that Celestia's cutie mark spell is remarkably close to an inference engine, similar to a declarative programming language. He goes on to model magic as an imperative language, and even proves that magic is Turing complete within the universe!
Fallen Hero: Here, the hero who falls is Princess Celestia, whose Fatal Flaw is her supreme confidence and pride. When faced with the decision to either admit her failures or continue on her path, she invariably chooses to continue doing things her way. During The First Equestrian Civil War, this eventually leads to her destroying the entire town of Ponyville to teach ponies that revolution is futile.
Great Big Library of Everything: The Imperial Archives in the Empire's capital city of Concordia preserve all accumulated knowledge for the entire Earth, stretching back more than six thousand years before ponies even evolved.
I Lied: Celestia gives us one of these after tricking Princess Luna/Nightmare Moon into activating the Elements of Harmony with her. (For context, all Luna wanted was for things to go back to the way they were before the monarchy, so Celestia promised to use the Elements to reverse the spells she was holding the population in check with).
Les Collaborateurs: Ascending Star presents the so-called sham court: ponies that recognized Discord as the rightful King of Equestria in exchange for marginally better living conditions. Seeking his favor, they send spies throughout the population in an attempt to find the leaders of the La Résistance.
Magic A Is Magic A: The story makes clear several rules concerning the way unicorn magic works. Most important is the distinction between magical power and magical complexity. While any unicorn, regardless of study or skill, can cast simplistic spells (such as the standard telekinesis), and can cast very powerful versions of these spells when properly motivated (i.e. being able to lift large objects or throw items with great force), skill and instruction are required to master complex magic. So only a pony that has studied extensively can work with transmutation, teleportation, time spells, thought control, etc.
Meaningful Name: Celestia's birth name, Celeste, obviously shares a root with the name that she will adopt for herself.
This is however, inverted for Princess Luna, as her birth name, Claire, has absolutely nothing to do with the moon. There is a famous French song called "Au clair de la lune", which in English translates to "In the light of the moon," but that was probably unintentional.
The names of all the Masters from Act I are indicative of their chosen elements: Terraria = Earth, Aquos = Water, Seraph = Fire, Altas = Air.
The name of Discord's capital city in Act I, Eridian, references Eris, the Greek goddess of discord.
Mother Nature, Father Science: in Act I, the two female Ancient Masters command the orders most in tune with the natural world. Terraria seeks unity with the natural order, and Aquos tries to control her world through understanding magic. The two males, by comparison, are far more rationalistic in their goals. Altas is a mathematician, and Seraph is an industrialist who seeks to rule nature.
Not So Different: when Celestia meets Discord for the second time in Act II, he reveals that he was once a unicorn like her, but was driven to accept the power of dark magic when his whole family was killed in a meteorite strike. Over time, the dark power consumed him, turning him into the creature he is today.
Romanticism vs. Enlightenment: the conflict between The Emperor (Enlightenment) and the citizens of Equestria (Romanticism) is clearly one of these. The Emperor favors a completely technology-driven society, built on the principles of mechanization and a rigid social structure. The inherent ideals of the ponies instead favor a more communal and friendly society.
Technology Is Evil: the villain of Act I is a mechanical genius who uses his talents to invent new forms of weaponry and munitions.
When Celestia assumes the throne, she goes so far as to explicitly declare that technology is evil, and strictly bans its proliferation.
This Is Something He's Got to Do Himself: happens once in Act I when Celestia goes to get her revenge on Seraph, after he tries to kill her and assume the throne. All it takes is one look for everyone else to realize that she does not want help.
The Corruption: the unnatural blending of light and dark magic that is Celestia's cutie mark spell functions this way for the Everfree forest, slowly twisting it from a beautiful, peaceful place into the corrupted strangeness that it exhibits in the present.
The Man Behind the Man: when Celestia and Luna first defeat Discord in Act I, his boss The Emperor shows up later in the day to offer them an ultimatum, allow Equestria to integrate with his Great Empire, or else he will destroy them and repurpose the land as needed.
Was Once a Man: Discord reveals in Act II that he was originally a unicorn, before being driven to accept the power of dark magic by Survivor Guilt after a meteorite strike killed his entire family. Over time, the power corrupted his form.