The sky was clear: not only of clouds, but of the moon yet-to-rise.

A single black shadow moved between earth and twinkling stars. This shadow also glittered faintly, and whispered like smoke. The smoke-cloud zigzagged through the air; it’s destination: Canterlot Castle.

The night-guards on the battlements took no notice of the cloud as it flittered down into a paved, three-sided inner courtyard. As the cloud touched the earth beneath the end-wall, it swirled and gained substance, revealing a larger-than-average black-bodied alicorn carrying a regular-sized lavender alicorn, the latter slung across the former’s back.

“Awake, Twilight Sparkle,” Nightmare Moon hissed. “We have arrived amid the ivory towers of your youth.” She tapped her left hoof twice on the ground. “Up.”

Twilight Sparkle pushed her forelegs into Nightmare Moon’s right flank and slid down her left. When she landed on her haunches, Twilight remained hunched.

“I believe I said ‘up’; that would be ‘down,’” Nightmare Moon stated archly.

Twilight did not reply.

“Rise, Twilight.”

Twilight pushed herself upright, trembling only slightly before steadying all four hooves. “Why are we here?” she whispered.

Nightmare Moon ignored her. Twilight frowned. “Look at me.”

Nightmare Moon whipped her head around sharply, glaring into Twilight’s eyes, their muzzles all but touching. Twilight’s own eyes narrowed minutely, exhaustion pushing her beyond caring.

After a moment, Nightmare Moon smirked and withdrew her head slightly. “My, my; after all this, you still have a strong spine in you.” She faced forward. “Come.”

Nightmare Moon began to walk, away from the rear courtyard wall and towards the open side. Twilight followed a heartbeat later, head low.

“Nightmare, why are we here?”

“You know, I promised you knowledge; you ought not look the gift-horse in the mouth.” Nightmare Moon turned about and moved closer to Twilight. She reached her head down and began to softly but firmly lick Twilight’s neck above her shoulder, running her tongue over two small punctures. Twilight fell to her haunches, eyes screwed shut, something like a whine and a sigh escaping between her lips.

“Does that feel better?” Nightmare asked quietly. Twilight sighed in response. “Good.” For a moment, Nightmare Moon’s face softened, but Twilight missed it as her eyes were still closed.

Nightmare Moon turned about and swatted Twilight’s left flank with her tail. “Move, Twilight Sparkle; we have work to do.”

Nightmare Moon began walking again, faster than before, and Twilight had to trot to keep up, falling in at the Nightmare’s left flank.

“This is a night for subterfuge, Twilight Sparkle. Tonight, you will take the first step in fulfilling your true power.”

“But, Nightmare, why are we sneaking around? I mean, if I’m going to ascend, shouldn’t I share it with Princess—”

Nightmare Moon glanced back at Twilight before turning about and dropping to her knees. “Twilight, this is about you. You know Celestia will not understand. That is why we are here now; Celestia will be asleep.”

“But what about Princess Luna?”

Nightmare Moon snorted daintily. “Like as not, she will be busy with the Night Court—notice how the moon has yet to rise? It seems she has more than a few petitioners this night; this is a good chance to avoid her: even if she is awake and active, she will be distracted. Come; let us not waste time.”

* * *

“Here we are.”

Twilight swallowed as she sat peering around the darkened corridor before the Canterlot Archives. “And why are we here? In the dead of night? Unannounced?” Twilight asked flatly, her ears mirroring her voice.

“I recalled something recently,” Nightmare Moon replied calmly, “something fragmentary, a memory of my time shared with Luna. It’s vague, but it has to do with unicorn magic, its ebbs and flows.”

Twilight’s ears snapped forward; Nightmare Moon smiled at that. “Aha, that’s all it took.” Nightmare Moon stepped forward and placed her right hoof on the right-side to the Archives; she stroked it, and it opened with but a whisper. “Enter.”

Twilight rose, and took a deep breath. “Mmm, dust, ink, paper.” She trotted through the doors; Nightmare Moon followed, and closed the doors with her magic.

“So, this book…?” Twilight was already trotting around the stacks, looking left and right, a faint purple light bobbing on the tip of her horn to illuminate the books’ spines as she skimmed them. She pulled one out with her magic, peered at it, and put it back, disinterested. “Is it…”

Twilight stopped moving, then slowly turned to face Nightmare Moon, who remained standing impassive by the doors. Twilight walked back towards the Nightmare, ears flat. “Nightmare, come on. We’re here, so we might as well do this. What are we looking for?”

“It is a spell of magical enhancement and replenishment.”

Twilight tapped her left hoof. “Okay… I guess since you’ve been using my magic, that’s kind of obvious in retrospect—”

“It is forbidden, of course.”

Twilight’s ears snapped forward, and her eyes widened in surprise. She raised a haunch. “Oh, and why’s that?”

The Nightmare stepped forward. “Because, like all magic, it has its price. There are many methods to increase magic, but they all boil down to two ways: One is to take more of the user’s own life; the drastic increase of the basic unicorn casting technique. The other is to take life from others.”

Twilight skittered back at that and fell on her rump. “W-w-what?! But that’s—That’s exactly what Tirek did to us!”

“True,” Nightmare Moon replied coolly.

“Bu-bu-but it’s wrong!” Twilight cried.

“And yet Tirek achieved power.” Nightmare Moon stalked forward, nostrils flaring, forcing Twilight to scuttle back into a stack of books. “Do you think his desires are so far removed from yours? Are you different?”

Twilight’s eyes snapped into narrow focus. She grimaced, pushed her way upright, and set her jaw. Lines of power—mainly purple, but with wisps of other colours—trickled across her body and into her horn. “I’ve had enough of you,” she growled. “I don’t care anymore. You won’t make me turn against the ponies I admire most! Nightmare Mooooooon!”

For an interminable instant, Nightmare Moon stared into Twilight’s eyes; then, she lowered her head and turned away. “Well done, Twilight Sparkle.”

Twilight’s magic instantly dissolved in a puff of smoke. “What?”

“Art thou not great? Art thou not unlike thy mentor, Celestia? Art thou not Princess Twilight Sparkle, alicorn, Element of Magic? Hast thou not the strength of mind, will, and body to defeat any challenge? And yet, thou art a depressive, moping little filly, allowing one such as I to drain her. WHY?!”

Twilight blinked. “But… how… Of course I would be down! You’ve been stealing my—”

“NEIGH, FOAL!” Nightmare Moon’s voice echoed. “I have not."

“But you said you would trade knowledge for my magic!”

“I lied.”

Twilight sank to her belly.

“Well, in truth, I fibbed. No, Twilight Sparkle, I was not stealing your magic. I took but small amounts; truly small, only such that you would feel it. But the greatest drain on your magic was yourself.”

Nightmare Moon turned back to face Twilight. “The truth is, you are empty, are you not? You faced Tirek, stopped him as he stole the life from ponies. You took in the majesty of four alicorns and pitted it against the power of every pony within this nation. And Discord,” she added disgustedly.

“And you had to give it all up to a conqueror, before you could claim the Rainbow Power, something yet greater than the Elements of Harmony.

“And where are you now? Your precious library a smoking ruin. A cold castle made of glass. Who supports you? Celestia and Luna, sisters, they rule the skies; dear Cadance, she spreads love, and has a stallion by her side, your own brother Prince Shining.

“What is your domain, Twilight Sparkle? Are you the Princess of Friendship? How will you spread this magic… with no one by your side to love you?”

Twilight began to cry.

“Do I speak truth, Twilight Sparkle? Do you long for one to stand by your side?”

“Yes…”

“And then, there is the Nightmare Moon. What is my domain, I wonder? What shall I rule and covet and nurture? For whom… shall I be strong?

“Twilight Sparkle, I am no longer evil, but I am not anchored by love. I will not deny, and I never did: I want what Luna has. She coveted what Celestia had. You too coveted what Celestia had; it is what made you strive for greatness. You need only somepony by your side.

“Will you let me bear you up to greatness? Will you tame the heart of darkness, and release the Nightmare?”

Twilight looked up. Nightmare Moon regarded her before slowly turning away.

“Consider one thing, Twilight: When I first appeared to you and began to drink your magic, the moon was a waxing crescent. Like the moon, my power was small, but it was ready to grow. Throughout these last two moon-cycles, my power has grown with you.

“Tonight, you will see the waning crescent. Like the fading moon-light, my hold over you has diminished through your realization. My last caress to you tonight—a nuzzling, to lick your wounds—was all I could give back to you… for now.

“Consider my words, Twilight. I promised to take your trust and not betray it; it was a test for me as it was for you. It is in your power to decide whether either of us pass.”

Nightmare Moon faded from sight, leaving Twilight alone.

* * *

Late that night, the tiny sliver of the moon passed by one of the Archive’s windows.

A second moon—though in truth, a dark-bodied alicorn—entered the Royal Archives and skittered when she noticed she was not alone: a small lavender alicorn lay upon the floor.

“…Twilight Sparkle? Pray thee, what bringest thou here among these dusty shelves? Dost thou also desire the deep quiet? We are delighted, if perplexed, to welcome thee.”

“Princess Luna… I need to talk to you.”