Highlight this box with your cursor to read the spoiler text.
The beginning of the end for Equestria was... a field trip to the former Canterlot Sculpture Garden.
Three friends, who were once known as the Cutie Mark Crusaders to themselves and their peers, had gotten into a bit of a dispute about trivial things, such as the validity of the word "victoryful" and the symbolic meaning of a draconequus statue (which began to pulse and crack at the discord they caused). After being scolded by their teacher and instructed to write a paragraph or five on the subject of discord, the Crusaders followed the rest of the group on their merry way to a different part of the sculpture garden, as the draconequus statue laughed an ominous laugh and cracked utterly.
The draconequus statue had been the stone prison of Discord, the god of chaos and disharmony who had ruled Equestria in a state of unending chaos millennia before. Two alicorn sisters, Celestia and Luna, had put a stop to Discord's terrible reign after discovering six powerful sources of magic which eventually became known as the Elements of Harmony - honesty, kindness, laughter, generosity, loyalty, and magic. These Elements were the only sources of magic more powerful than Discord, and so using them, Celestia and Luna sealed Discord within stone that could not be penetrated by his black magic, trapping him forever and finally bringing order to Equestria.
However, after Luna was corrupted by an entity known as Nightmare Moon and banished for 1,000 years to the Equestrian moon, the connection between her and her sister, and the Elements, was broken, loosening the bonds that held Discord's prison together. 1,000 years later, when six new ponies rediscovered the Elements and used them to rid Luna of Nightmare Moon's influence, the spell was weakened even further. Finally, the prison got so weak that three feuding fillies were able to crack it open utterly and release Discord once more.
After a brief tussle with chocolate milk-filled cotton candy clouds in their hometown of Ponyville, the six ponies who bore the Elements were called to Canterlot by Celestia, who warned them of Discord's return and ordered them to stop him once more with the Elements, which took on the form of decorative jewelry after the Nightmare Moon fiasco and were locked behind a powerful magical barrier in Canterlot Tower, which in theory, only Celestia could break. When they found the Elements missing, however, Discord revealed himself through a series of amusing stained-glass images, explaining that he took the Elements. He gave the ponies a cryptic riddle - "Twists and turns are my master plan, then find the Elements back where you began" - which led them to the palace labyrinth, right next to the Sculpture Garden where Discord's stone prison had been kept. Right into Discord's trap.
He had intended for the ponies to enter the labyrinth, just so that he could wreak his magic on them - essentially "Discording" them. After taking the wings and horns of the pegasi and unicorns in the group to ensure that nobody would cheat in their "little game", and letting them know that unless everyone played, the game was over and he won, he separated them at the maze's entrance and picked them off one by one.
Applejack, bearer of Honesty, was turned into a compulsive liar - not to mention a BAD one - after visiting the "Grove of Truths" and seeing a terrible vision of the six ponies ending their friendship. Pinkie Pie, bearer of Laughter, became deadly serious and loathed everything thanks to a garden full of balloons - some of which took on the forms of her friends - laughing at, instead of with, her. Rarity, bearer of Generosity, began obsessively and selfishly hoarding a "diamond" (really a cheap boulder disguised by Discord's illusions) she found in the maze. Fluttershy, bearer of Kindness, at first resisted Discord's magic until he finally got so fed up he just tapped her on the head and turned her into an absolute brute. Finally, Rainbow Dash, bearer of Loyalty, took back her wings from Discord and abandoned the game, breaking both of the rules Discord set. Only Twilight Sparkle, bearer of Magic, was left uncorrupted. Discord took a minute to destroy the labyrinth, taunt the five remaining ponies, and laugh at Twilight for getting the riddle completely wrong before heading off to Ponyville to begin wreaking disharmony.
After thinking about the riddle, Twilight came to the conclusion that the Elements were hidden in Ponyville, hence "back where you began". While she was eager to simply get back to her library, read up on the Elements, find them, and seal Discord back up, her Discorded friends did everything they could to delay that. After a brief battle during which the four Discorded ponies played a game of keep-away with the reference guide to the Elements, Twilight opened the book to find... the Elements, hidden inside! She took a moment to slap the Elements on her Discorded friends (with her dragon assistant, Spike, becoming a last-minute stand-in for the absent Rainbow Dash) before putting on her own piece of Element jewelry (which, unlike the necklaces that were the other Elements, was a rather large crown) and moving outside to confront Discord. As she stepped outside (along with "Tom", the name Rarity had given to her "diamond"), she heard Discord's mocking voice...
"Well, well, well, I see you've found the Elements of Harmony. How terrifying!" Discord almost seemed to be enjoying the fact that his adversaries had found the only things in Equestria that could stop him. As the four Discorded ponies stared at their necklaces in contempt, Twilight stepped to the front of the group, facing Discord. "Discord! I've figured out your lame riddle!" Almost as if to reassure herself, she yelled, "You're in for it now!"
Discord, the ultimate troll, went along with it. "I certainly am. You've clearly outdueled me, and now it's time to meet my fate." Just to be even more of a troll, he summoned and wore a pair of sunglasses and created a bullseye in front of his torso. "I'm prepared to be defeated now, ladies. Fire when ready!" Twilight tried to muster her Discorded friends into action with a valiant cry of "Formation. NOW!", but that only got a collective "meh" out of them. Turning to the rock Rarity called Tom, Twilight yelled, "Rainbow Dash, get over here!" Spike, who had been hiding behind Tom, swallowed once and stepped out to join the group. "Alright. Let's get this over with!"
A familiar breeze whipped through the street as the Elements activated. Twilight levitated into the air with glowing white eyes as a powerful white light emanated from the gem on her crown. The four other ponies rose into the air and were surrounded by similar light as the Elements worked their magic... or not. Before the burst of magic that would seal Discord could be released, the Elements ceased their magic. The light shut off and the five ponies fell to the checkerboard-patterned ground.
Bewildered, the four Discorded ponies began to insult and disrespect their Elements, tossing them to the ground, stealing them from one another, lying and arguing about which ones worked and which ones didn't, and generally cursing their name. Spike, knowing he was of no use at the moment, decided to leave, placing the Loyalty necklace on the ground next to Twilight and returning to the library to do some cleaning. After being tripped up by Fluttershy, he heard Discord gloating behind him, so he picked up the pace and got back to the library as fast as his little dragon legs could carry him.
As soon as he got back inside the library, he saw a blinding white flash and Discord appeared before him, standing in the middle of the room. "Ah, Spike, Twilight's little helper. How rude of me to watch you try to seal me in stone without introducing myself. I'm Discord, god of disorder and unrest. I'm sure Twilight's told you all about me." All thoughts of cleaning up the place vanished as he launched himself at Discord. The latter simply encased Spike in a field of energy, stopping him completely in midair.
"Oh, Spike, I can't have you doing that. Though I do find your loyalty admirable - perhaps you could've stood in for Rainbow Dash after all, if only you had been touched by that 'spark' of Twilight's during the Nightmare Moon fiasco." Being reminded of his Rainbow impersonation made Spike shiver within the energy field. "Rainbow would kill me if she found out (don't get any ideas)... Twilight thought I could just wear that little Loyalty necklace thing and fill in for Rainbow, but eh. What does she know?" Discord grinned and lowered Spike to the ground, dissipating the energy field in the process.
"Ahaha, well put, Spike! If the circumstances were different, I think you and I would make excellent friends. But as it stands, I am the immortal, omnipotent, malignant god of turmoil and disorder, while you are just the Element of Magic's doormat." That got Spike's attention. "D-doormat? How do you figure I'm Twilight's doormat?" Discord drew himself up to his full height and stretched his disaccorded arms out for dramatic effect. "You cannot deny that you were born into slavery, Spike. Twilight hatched you as part of her entrance exam for Celestia's Magic Academy, and ever since, she's been working you around the clock for tasks she could do herself - and with far less effort - by 'waving her magic little horn'. Why should she be working you to the bone, Spike? And why should you stand for it?"
Discord summoned a massive pile of gemstones in the center of the room, all of which began to reflect a series of images. They showed Spike what had happened to other helpers, or "doormats" - abuse, mistreatment, overworking, the whole nine yards. The vision faded after Spike was shown one last image, of an older, more time-worn version of himself, frazzled to the bone by years of helping Twilight. Swirls formed in Spike's eyes and he let out a bigger "NO!" than he had when his love, Rarity, had been kidnapped by thieving mutts during a gemstone dig. Discord stepped up to Spike and told him jovially, "You see, Spike? Letting Twilight and everyone else walk over you won't get you anywhere. You have to live for yourself, be your own dragon, live life as YOU say you should, not as Twilight says!"
The swirls in Spike's eyes disappeared as his colours desaturated and he jumped selfishly into the pile of gemstones, devouring them one by one and not even thinking of how they could help Rarity at some point. "You know what? You're absolutely right, Discord! How could I have been so foolish as to let Twilight do this to me? From now on, I'm looking out for me!" Summoning a red parrot into existence for no reason other than that he could, Discord clapped his hands, creating a symphony of sound effects in the relatively small library. "Well done, Spike, you're learning! We shall have to talk again sometime. Now while we're talking about Twilight and before I forget, I simply must go inform Celestia of your former master's... condition." Executing an expertly timed pirouette straight up into the air, Discord flashed out of existence, leaving Spike alone with the gems.
Before long, Spike felt a familiar tingle in his stomach. He belched green flames and a scroll appeared before him. Perplexed, he picked up the scroll and began to read. "Dear Princess Celestia, I've learned that one of the joys of friendship is sharing your blessings... Hmm, this sounds familiar. One of Twilight's old friendship reports?" As he wondered why Celestia would send it back, he received another scroll, containing another friendship report. "Hmm... Wait a minute. Discord said something had happened to Twilight and he was going to tell Celestia. She must be sending these letters back to help Twilight! I won't stand for this!" Before another friendship report could be received, Spike took the quill from the inkstand on the nearby pedestal Twilight used for writing and a blank sheet of paper, and jotted down a quick reply. "Dear Princess Celestia, I'm terribly sorry, but Twilight will not be able to receive these letters. I will send all the ones you've sent so far back to you soon. Regards, Spike." Satisfied, he rolled the paper up into a scroll and breathed more green fire onto it, sending it to Celestia. He then repeated the trick with the two friendship reports. "That's that taken care of."
At that instant, Twilight entered the library, completely desaturated and in a miserable mood. She instructed Spike, "Pack your things, Spike, we're leaving. And don't ask where we're going, because... I don't know yet. Just not here." She began to pack away a few books and threw her Magic crown into the nearest waste receptacle. In the sorrow she was wallowing in as she packed, she barely even noticed Spike fully desaturate, and definitely didn't hear his mocking reply.
"Pack them yourself."
And thus it came to pass that the spirits of the Elements of Harmony were broken, Equestria fell to Discord once more, the royal sisters Celestia and Luna were kept imprisoned in dungeons, and chaos reigned throughout the land. It had been two years since that fateful day, and Equestria only got worse with each passing day. Discord still loved the turmoil he had caused, but after only two years of it he had grown weary. He needed new excitement, new blood. Merely the deaths and torture of ponies wasn't cutting it for him. And it was thus that a devious little thought began to form in his mind. He summoned a quill and ink into existence and wrote quick notes about his plan onto sheets of tool steel. He stared triumphantly at the quill marks adorning the page and tossed the ink out the window of his castle, where it set fire to an unsuspecting aerial porker, dropping cooked steaks on the lands below.
Discord put his hands behind his head and leaned back on his obsidian-and-pony-leather throne, chuckling psychotically to himself. This was going to be a blast.