Princess Celestia sat comfortably upon her throne, sipping tea and listening to the sounds of activity about her. Cliques of government officials milled about the throne room; if she concentrated hard enough, Celestia could discern their individual conversations. She had known the various ponies in her administration for their entire lives, and the characteristic inflections and tones of their voices cued her in to who was speaking without the need for conscious thought on her part. Even the hoofsteps of ponies passing through the room could alert Celestia as to the identity of the pony, their current mood, and their probable destination.
Beyond the chatter of bureaucrats going to and fro in her presence, Celestia noted other sounds. She heard the thuds and crashes of attempted construction on one of the palace towers. She caught the soft swish of air as pegasi guards flew patrols and practiced maneuvers outside. She listened to the creaking of doors swung on old hinges, the rhythmic ticking of a stately grandfather clock, and an ever-present background hum that lay beneath everything.
Celestia also heard the pop of her sister materializing beside her.
“You know the guards feel nervous whenever one of us teleports,” Celestia said. She did not bother to look over at Luna, but merely savored the smooth slurp of another gulp of tea. “They seem to worry that if we are out of their sights for an instant, something tragic will happen to us.”
Luna tossed her mane in a careless shrug. “Then perhaps the guards should question the usefulness of trying to protect immortal alicorns who possess powers they can scarcely comprehend. I cannot fathom why you did not dissolve the E.U.P. hundreds of years ago.”
“Well, the soldiers were restless after centuries of peace, and there were only so many spots available in the Wonderbolts. I did not want to leave them with nothing to do.”
Luna snorted. “Surely there was some enemy they could have fought. In the years before my banishment, we seemed to encounter a new foe every other day.”
Celestia breathed in another sip of tea. “On the contrary. During the whole millennium you were on the moon, not one single villain tried to depose me, conquer Equestria, subjugate our little ponies, or plunge the land into a state of eternal mid-morning. It was really quite a boring time.”
“Please, sister,” Luna said. “You cannot expect me to believe that as soon as I was gone, our steady stream of adversaries was abruptly cut off. Why, pray tell, would such a thing occur?”
With a soft sigh, Celestia set down her tea. The cup emitted the faintest tap as it came to rest on its saucer. “I had hoped you would never ask me that, sister. The answer to that question is somewhat…delicate.”
“Delicate?” echoed Luna. Her hooves rustled uneasily. “Why would it be delicate?”
“You see,” Celestia began, shifting uneasily on her throne. The cushions beneath her produced the peculiar swishing sound of fabrics rubbing against one another. “The reason we had so many enemies before you were banished, and none once you were gone—well, the reason is you, Luna.”
“Me?” exclaimed Luna with haughty incredulity. “Whatever do you mean?”
“Think about it,” Celestia replied. “Before your vacation on the moon, we fought a new foe every couple of years. And since your return, Twilight and her friends have encountered all of our old adversaries, as well as a couple of new ones. But during the intervening thousand years, Equestria was inexplicably at peace. The only variable that had changed was your absence.”
“And just how am I responsible for every monster that has ever threatened Equestria?” growled Luna.
“Scholars debated the matter for centuries,” Celestia said with a conversational matter-of-factness. “Some theorized you had poisoned the dreams of our enemies as a prelude to your rebellion as Nightmare Moon. Others suggested evil creatures were naturally drawn to your darkness. Many experts simply gave up on trying to explain it and said it was lunacy.”
“Lunacy?”
“Yes. The word originated as the technical term for your insanity as bringer of the eternal night. Then some scholars started applying it to the crazy schemes of our other enemies. They seemed to think it was your influence that caused our adversaries to behave in such a manner.”
“So whenever I hear somepony use the word ‘lunatic’…”
“They refer to a pony who has been driven insane by your diabolical machinations. Though I admit that perhaps the technical definition is lost on many ponies in the present age.”
Celestia again levitated her tea to her mouth and drank a long slurp. Beside her, Luna noiselessly worked her jaw through all sorts of disbelieving contortions.
Finally, Luna managed to recover her voice. “And do you believe this madness, sister?”
“Of course not,” Celestia said. “While I have long been aware of the corollary between your presence and the national threat level, I do not in the slightest believe you are to be held responsible for the connection.”
Luna let out a relieved breath. “Thank you, sister, for your support. And have you discovered the cause of this apparent link between me and our enemies?”
“Yes, I have.” Celestia paused to scratch an itch on her side before continuing. “It is your mane.”
“My…mane?”
“Precisely.” Celestia stretched her neck to the side, waiting to hear the satisfying crack of gas escaping her joints. “Your mane constantly emits a magically-enhanced, high-pitched buzzing noise that tends to irritate other ponies. The more dark magic a pony possesses, the louder the hum sounds to her.”
“What?” Luna did not seem inclined to believe Celestia.
“Listen, sister,” Celestia instructed. She held a hoof to her ear. “Do you hear that continual humming in the background? Listen carefully.”
Luna dutifully fell quiet and listened intently to the noise around her. Her eyelids closed as she focused on separating the different sounds in the throne room and on isolating the steady background hum. A minute later, her eyes opened again and a frown formed on her face.
“That sound is coming from my mane?” Luna asked, hesitantly.
“Yes,” affirmed Celestia.
“And it sounds louder to creatures that wield evil magic?”
“Definitely.”
“So every opponent we have ever fought, every adversary that has ever endangered the safety of our subjects—they have all attacked because they cannot stand the sound my mane makes?”
“I am afraid so, sister.”
“In that case,” Luna said, rising to her hooves with a loud clatter, “I must be off at once.”
“To do what, dear sister?” Celestia asked in surprise.
“To shave my mane off.”
Luna vanished with a distinct pop.
“You summoned me, Princess?” asked a royal guard as he bowed before Celestia.
“Yes,” she said. “I need you to do something for me.”
“Anything, Princess,” he replied.
“I need you to go to Princess Luna’s chambers and leave on her bed a copy of Princess Twilight’s report on the Tree of Harmony,” Celestia said. “Make sure Luna will notice the report as soon as she returns.”
“The report detailing how the Tree protected the nation for a thousand years while slowly dying, and how recent instances of ponies wielding the Elements drained the Tree of its power and removed its protective spell from Equestria?”
“Yes, that is the one.” Celestia absently tapped her hoof against the throne as she spoke. Her mind was preoccupied with the considerate deed she wanted to do for her sister. “I think Princess Luna would be interested in learning what kept our nation safe during her absence.”
As the guard stood and turned to leave, something else occurred to Celestia. “Oh, and the choir that I hired to stand in the hall and maintain a constant, monotone hum? You can thank them for their work and tell them they can stop now.”