This is a story. A serious one. There may be comedy thrown in, but (spoiler alert) a vast number of ponies... kick the bucket, hop the twig, push up the daisies, feed the worms, assume room temperature and carry out many other euphemistic phrases blatantly stolen from Wikipedia. This is not a happy story. Try to enjoy anyway.
Grand Empress Celestia was becoming old. Very old. The once glowing solar princess was now a dusty husk, a shell of her former self. And whilst plenty of ponies throughout history, like Starswirl, Clover the Clever and (according to a recent poll) Mr. Cake had become increasingly wise and powerful in age (Mr. Cake's Arcane Pastries had been feared in their day), in the celestial ruler it was almost entirely the opposite. She had gone, like old people often do, completely and utterly insane.
However, the Elements of Harmony had done wonders for Twilight Sparkle and her multicoloured entourage. Their sustaining magic kept them young and now the six of them, who had defended Celestia's kingdom and leadership for so long, dared to oppose Celestia's tyrannical (if not slightly deranged) rule. This could not continue. And so whilst she was mumbling to herself about... things, perched on the throne like some seagull gone wrong, a certain pony walked into the Royal Throne Room. A very special pony.
His name was Haxail, he was evidently a pegasus, and that was all most people knew about him. Haxail was not the kind of pony you met for more than a few, rather painful seconds. He was the kind of pony not many people liked talking about, because death wasn't exactly celebrated in Equestria. Neither was Haxail. Yet he strode in, a darkish cloak swept across his back, complimenting his darkish grey mane and darkish grey eyes. Nopony had ever seen his Cutie Mark. Haxail knelt before the Grand Empress, who was now beginning to drool and said, "Orders, your Majesty."
Celestia mumbled something incomprehensible. As expected, Calcula stepped forward, grinning like a hydra on acid. It was not a nice look. Calcula used to be just a secretary (admittedly the only female one and Celestia's best) but the arrogant bitch now acted as a communicator, relaying the Empress's orders to the insolent worms that were her subjects. "The Grand Empress bids you 'good morning'," said Calcula. The stupid grin hadn't left her face. "And, the Grand Empress wishes to engage you in another... contract."
"What does... her majesty wish?"
Celestia mumbled a bit more. Her dentures slid out her mouth, and plopped onto the floor in their own private puddle of nastiness. Even Calcula grimaced, and turned to the nearest Royal Guard. "Clean that up."
The Guard looked pleadingly at his friend, who, in true Royal Guard tradition, did absolutely nothing to help. Calcula turned back to Haxail and continued with her undoubtedly faked "orders".
"The Grand Empress has been troubled for years now by the Twilit Separatists, which as I'm sure you know, is led by those insolent excuses for asinine equines, the Mane Six. Her Royalness needs them gone, as quickly as possible. Minimum mess. Are you up to it?"
Haxail snorted, and said, "I'm an assassin. I kill ponies. It's my job. So, yes, I'm up to it. Bitch," he muttered the last part under his breath.
"Thug," countered Calcula. There was no love lost between the two.
"Slut."
"Psycho."
"Tramp."
"Shut da fuck up!" Celestia gargled, speech slurred by her lack of teeth. Everypony whirled to stare at her.
"Yes your Royal Celestialness!" cringed Calcula. Haxail smirked. However, it took approximately 0.000023 seconds for Calcula to be back to her usual obnoxious self.
"Well, Haaaaxail," grinned Calcula, "You have your orders. Make things happen. Bye."
And with that, Haxail strode out, hooves clopping loudly against the floor.
Notes: Many authors put witty, interesting and relevant things in the "notes" section. However, as I have about as much creativity as a flattened shrew, this is seriously a mind-numbingly uninteresting notes section. So, yeah.