Prologue: Of Mail and Mares
In which Derpy plays goddess and dominoes begin to fall.

Celestia kept her face neutral but the facade was shallow, betrayed by muscles pulled taught and eyes that stared coolly at the cell door. The princess’s mane snapped and crackled in the still air, a roiling mass of self doubt and fear that churned the nebulous, rainbow-hued hair.

Was she right to allow a student, albeit one with staggering magical aptitude, to fight her battles for her? Was it right to risk Twilight’s and her new friends’ lives in the hope they could wield the Elements of Harmony?

When the Nightmare’s miasma had flooded the royal throne room, Celestia had capitulated with nought but a token display of force. The monster had been quick to believe the princess frail and powerless, but the reality was far from it. Celestia knew that her own powers were an order of magnitude greater than her sister’s, and that even now the thrumming magics keeping the cell closed would be easily shattered if Celestia willed them open.

But rather than break them apart sallying forth in blazing light, the princess kept her own magic sealed and stayed within her ‘prison’.

With so much of the Nightmare’s power and focus being directed at the prison, it would be unprepared for the Elements; unprepared for the Elements to be wielded by friendship rather than a desperate, lonely solar princess; unprepared for the Elements’ cleansing power, ridding Luna of Nightmare Moon’s influence and returning the princess of the night to sanity. All Celestia had to do while Twilight risked life and limb was to sit in a cell doing nothing.

It was torture.

AH, PRINCESS, I DO HOPE THE ACCOMMODATION IS TO YOUR LIKING? IT WILL TAKE A WHILE BEFORE THE LUNAR SUITE IS PREPARED TO RECEIVE YOU.

Shaken from her pensiveness, Celestia gazed at the nebulous black form just beyond the cell door, now open.

I DID WONDER WHAT SCHEMES YOU WOULD TRY TO STOP ME. IT IS ALMOST SAD HOW QUICKLY YOUR DISPARATE MINIONS FAIL.

What!? Celestia’s eyes went wide, and what little colour existed in her face drained away.. Surely she hadn’t miscalculated? If anything had happened to Twilight and it was her fault...

I FOUND THIS ONE IN THE FOREST SPYING. I THOUGHT SHE COULD KEEP YOU COMPANY WHILE I FINISH CEMENTING MY POWER. YOU WERE ALWAYS FOND OF YOUR LITTLE PLAYTHINGS.

A tiny body was tossed into the room, crumpling against the mildewed wall. Dropping all pretense, Celestia galloped across to the motionless form and knelt to inspect it closely. It wasn’t a unicorn, so it wasn’t Twilight. Celestia offered a silent thanks to the heavens that her student had yet to be captured, and was then wracked with guilt at being glad that pain had befallen another in Twilight’s place. Pushing such thoughts aside, the princess ran a hoof over the body to find a beating heart, steadily respiring lungs, bruised but otherwise undamaged wings, and no injuries beyond superficial cuts and bruises.

Twilight wasn’t a grey pegasus, and neither were any of the ponies the princess thought she would befriend, but what if Twilight had started a friendship with this one over one of the other five? Could they have been captured so quickly and her plan undone?

YOU ABASE YOURSELF BEFORE THIS CREATURE, CONCERNED WITH ONE INSIGNIFICANT MORTAL RATHER THAN YOUR OWN SISTER!? YOU TRULY ARE AS PITIFUL AS I REMEMBER! YOU ARE NOT FIT TO BE A PRINCESS...

The last line was a hiss of bitter contempt, and with that the cloud turned and left, slamming shut the door in its wake. Not that Celestia noticed, her attention was still focused on the pony. The princess had picked five ponies with temperaments suited for the elements, but none of them had been a grey mare. Twilight could have befriended others, but then why would the pegasus be on her own?

Eschewing magic lest the Nightmare see through her ruse, Celestia set to work licking wounds clean and massaging muscles so the pony would not wake stiff or in pain. Before long her work was done, and the princess curled round the pony to keep it warm with her body heat.

“Hurry, Twilight.” Celestia whispered before closing her eyes and falling into a restless sleep.

“Mmrglm...just don’t know what... wrong...”

The princess stirred, woken from fitful slumber by the mare.

“Hush now. You are safe, my little pony.”

The pegasus struggled upright as memories of her encounter with Nightmare Moon trickled back, but the motions ceased when Celestia placed a forehoof on the pony’s chest.

“Do not strain yourself, my subject. For the time being we are prisoners, and panic will do neither of us any good. Tell me how you came to be in the forest?” Celestia could still see wariness written in the mare’s eyes, and it dawned on her that waking up in a cell with your princess might cause considerable distress. Being entrapped by Nightmare Moon and watching the sun fail to rise on their own would be difficult. Hardships were few and far between in Equestria, and although the princess had seen many in her time, it was only due to her nigh immortality. She realised that even stuttering would be beyond most ponies in the same position.

Discarding her mask, Celestia’s eyes softened and she willed soothing warmth to her voice. “Ah, where are my manners? What is your name, my little pony?”

“Th- they c-call me Derpy Hooves, your majesty.”

“Ah, a beautiful name. The Hooves in Canterlot have had a long history of keeping our postal service running like clockwork, and I’m honoured to share a cell with one.”

Celestia suppressed a chuckle as Derpy’s cheeks coloured slightly.

“T-thanks Princess! I work in the post office in Ponyville, I got something to deliver in this forest but that’s when I-” The colour drained away again, and Derpy looked around in horror. Patting herself down for the mailbag she’d been carrying. “The mail! She took it!”

Starting upright, the pegasus rushed across the room with her wings fluttering wildly, skidding to a halt at the locked cell door. “She... the letters...”

“What happened, Ms. Hooves?”

“I...” Derpy turned and sniffed, tears trickling down her cheeks, “I was late picking up my mail bag ‘cause I had some stuff to do for the Summer Sun celebration. I picked up my mail late, and after posting a few letters in Ponyville I came out to the forest to deliver a mail-order moustache-waxing kit to the forest.”

Focused on the story, and reassured that there was no indication the grey pony bore an element of harmony, Celestia absentmindedly wiped the tears from the mare’s eyes. Derpy took the proffered hoof and blew her nose on it loudly.

And wetly.

Celestia tried not to grimace, and as Derpy continued with her story wiped the worst of it on the floor while the pegasus wasn’t looking.

“I was flying above the trees when that big cloud thing came after me... I tried to get away, but my mailbag got tangled with a tree branch when I was distracted and... and I lost it!”

Derpy wretchedly lifted the loop of fabric round her waist, and Celestia saw the buckles and attached torn straps where a mailbag would have hung. “It’s the first time I’ve not delivered mail, I can’t lose them! I’ve never even been late! I’ll... I’ll be thrown into a dungeon, or banished, or banished and thrown into a dungeon in the place that I was banished to, and I bet they won’t even have a post office so I’ll have to find a new job and...”

“Silence, Derpy.” Celestia gave the pegasus a stern look for a moment, and then let the corners of her mouth twitch upwards. “You’re already in a dungeon, and as ruler of Equestria I shall forbid anypony from banishing you.”

Derpy’s smile returned, and remembering something went back to scrabbling at the belt, pulling at it until a small satchel came into view. She pulled out a carefully wrapped muffin and a small wooden box. Upending the box sent a wave of rectangular wooden shapes cascading over the floor.

“I like to stack the dominoes and watch them fall when I take a break,” Derpy gestured at the shaped now lying on the stone cobbles, “do... do you play your majesty?”

Celestia winked conspiratorially at the pegasus. “Of course I play...”

Celestia felt the backwash of magic as the Elements of Harmony were activated, revelling in the knowledge that her student was safe, Equestria saved, and her sister... her sister returned to the world, now rid of the festering darkness.

The princess stood up slowly as if in a dream, trembling slightly. Her legs suddenly gave way and she staggered forward, stopped from falling only by Derpy rushing across and leading against her. It... it was overwhelming. She would finally see Luna; not the snarling ebon mare or that black cloud, but her sister... it, it had been so long...

“Princess? Are you... ?”

“I am... I am fine, thank you Derpy. Much more than fine even, but I am afraid that I must be going now, I have a very, very old and dear friend to see. Please, will you come with me? It would honour me to have another witness this reunion...”

The mailmare started to nod, but then glanced behind her out the window and smiled apologetically.

“I should have been back at the post office by now, and I don’t want my friends to worry.”

“I understand. We all have our commitments.” Celestia nodded solemnly, but then a mischievous smile lifted the corners of her mouth. “Can I at least have your promise that we’ll play again? I would liked to have bested you once at least.”

Penny Black hit the ground, lying prone against the titled floor to avoid having her head taken off by an voracious newspaper. After dodging a sudden burst of chocolate rain on her way to work, the postmistress had spent a productive morning sorting paperwork and had settled down with a mug of tea and hay sandwich before the tabloid had sprouted fangs and leapt upwards, vociferating its headlines in a garbled hiss like the rustling of paper.

“Truth or Trixie: The Shocking Expose on Hoofington’s ‘Ursa’!!!”

The last postmistress had retired after Nightmare Moon’s reign of terror - more a light shower of irritation really, reflected Black - had caused chaos throughout Equestria, and Penny had been the mare to step up and take control of the post office. A cushy job in some backwater village, with a regular coach to Canterlot and a train that could go almost anywhere else? Of course she’d taken the job!

“Zecora: ‘Innocent’ Hermit, or Evil Witch Doctor? You Decide!!!”

But then there had been the “baked bads” incident that left most of her mail ponies in bed with food poisoning; a rampaging Ursa Minor that had destroyed a significant portion of the town, including the mail office; parasprites that ate everything the Ursa hadn’t; a sleeping dragon that caused severe delays with deliveries after rendering the sky unnavigable due to thick smoke; not to mention impromptu iron pony competitions, surprise fashion shows and unannounced royal visits...

“Cockatrice Attacks At Record High, First Petrification In Years!!!”

...and now there were pink cotton-candy clouds raining chocolate milk from on high, twisted lagomorphs with slender equine-like legs, and anything not nailed to the ground had started developing sentience, and an appetite.

“Were You at the Disastrous Grand Galloping Gala? Write in and Receive Ten Bits!!!”

“Ah! Get back! Shoo!”

At least they hadn’t grown teeth, but from Express Delivery’s wails the tills were making a good go at mastication regardless. One of the post boxes was making contented sighs and belching noises with Frank’s tail and hind-legs thrashing frantically as they disappeared through the slot, and Penny could have sworn that his rump was plastered in growling stamps.

Startled by the creaking of timber the postmistress turned, and found herself frantically backpedaling from a multitude of large packing containers, either bound to or arrived from distant lands. Trapped against the desk she’d just cleared of voracious papers, Penny Black had time for one last thought before everything went black and the menacing wall of crates thundered inwards.

Death by shipping was not how I wanted to go...

The groan of twisting wood and nails stopped, and when Penny cracked open an eyelid she was surprised to see the post office rather than the great sorting office in the sky. The containers that had been so intent on devouring her were now scattered across the ground, shattered and broken husks.

Sticky crimson ichor leaked from holes in a large crate bound for Ponyville’s resident jam lover, and Penny did her best to avoid it while stepping over piles of uncoiling fire hose and crimson-slicked rope to get a better view of what was happening. As the postmistress clambered out from among the ruined boxes, the closest one shuddered slightly and with a final sigh spilled the last of its packing peanuts onto the ground.

In the centre of the room stood Derpy, hugging... something. It looked like a mail sack, except it appeared to have a variety of large and dangerous looking teeth sown into it... and was that a dragon scale on it’s head!?

“The bag came back!” trilled the mail mare, manic glee in her voice, and moments later was flying out a nearby window to presumably deliver whatever was in the sack.

It took Penny a while to make sense of everything, and she soon set about rescuing her staff members, tidying up the post office, and filing for either retirement or a posting far, far away.