A drop of fuel for a Nightmare.

You opened your eyes. Then you closed them, and opened them again - they didn't seem to be working. It was still dark. A pained look outside told you the sun had already set.

Groaning, you awkwardly reached around for your lamp, swinging at random until your hand brushed against something you could use to find it. Hitting the button, the light sprung into life, illuminating the room.

It had been several days since your arrival, and you'd slowly become more acclimatised to a nocturnal sleeping pattern, in preparation for your new job as Princess Luna's manservant slash friend. As close to "friend" as you can get when you're being paid to do it, anyway.

Stumbling slightly as you arose from your warm, though still uncomfortable and absurdly undersized bed, you made your way to your wardrobe and pulled out a set of clothes at random. It was time to start the day - or rather, night.

Given the late hour of your awakening, your first order of business was to visit Celestia and tell her you were ready to begin, your schedule now as inverted as it was going to get.

"Oh, wonderful!" Celestia exclaimed, stifling a yawn and shifting her wings slightly under her thin yellow nightgown after you eventually found her preparing to sleep in her royal chambers. It took a lot of explaining for the guards to allow you access, but they seemed to know you were coming.

"Follow me and I'll introduce you both, then!" she continued, walking out of her chambers still wearing two pairs of soft, pink hoof slippers rather than her usual attire. Her hair, normally left to float freely in the air, was tied back and resting against her neck, much like anypony else's mane would be. The princess of the day looked far less intimidating during the night, looking more like an oversized unicorn than an indomitable goddess.

"Now, I should warn you, my sister is having a lot of trouble adjusting to all the changes. I trust you will be sensitive and try not to offend her," she warned as you walked, taking the short journey back to the hallway containing both your and Luna's accommodation. "Unfortunately, she and I disagree on a great many things, and without her influence the kingdom has strayed from many of her ideals. Please try and remember, she means well, even if she has difficulty showing it."

Celestia's words were worrying - when you'd been warned about her 'struggling to adapt', you'd assumed that meant shy and reclusive, but that description sounded like anything but. Celestia almost seemed concerned for your safety, though you were sure she would never put one of her subjects at undue risk.

Celestia knocked on Luna's door with a hoof, rapping against the wood three times. It was answered with silence.

"Luna? It's me, open up!" Celestia called through, banging on the door once more and trying to get her sister's attention.

A moment later, you heard the sound of metal grating against rock as the door was unlocked, and opened, by one of Luna's personal guard. Unlike Celestia's bright white pegasi, Luna's guard had a dark coat, and a pair of fragile, batlike wings. He - it? - stared at the two of you unemotionally, its attitude seeming every bit as unnatural as its body, filling you with a sense of dread. Some of the legends you'd read of Princess Luna's Night Guard, from back before her banishment, read like horror stories - you were shocked that such things could still happen now.

"My princess." it spoke, keeping its words curt and its voice level, "Princess Luna is occupied at present, though of course she will make an exception for you."

"Thank you, Shadow." Celestia replied, naming the pony and putting him at ease. He relaxed, and his wings folded back to his side as he bowed and retreated to let you pass. Without the unpleasant wings, he looked much like any other guard, just darker. Stepping back, he seemed to fade into the shadows as Celestia walked inside, tutting as she began to walk up the spiral staircase leading to Luna and lighting each dormant candle she found along the way, lighting up the path.

Bowing slightly to the guard as you passed - is that what you were meant to do? You supposed you were on about the same social level, now - you hurried after Celestia, not wanting to be alone in this unfamiliar area.

At the top of the staircase was another set of huge wooden doors, presumably leading into the main room of Luna's tower. Celestia's horn glowed, and the two doors smoothly swung open, slowly revealing the vast chamber that made up the majority of the tower. The far side of the room consisted of a huge pair of windows, currently open to the night. The two visible walls were adorned with bookshelves, the sheer quantity probably rivalling some small fraction of the main Canterlot library itself. Punctuating the bookshelves were several doors leading off into other rooms, and the centre of the hall was filled with a large table, surely capable of seating dozens of ponies with ease.

The one creature in the room was Luna herself, facing away from both of you as she hovered in the air, staring out into the night sky as she stretched her hooves around, moving and shifting areas of the starscape to better suit her mood. A few moments later, she nodded softly to herself and slowly dropped to the ground, seemingly pleased with her work. Her hooves struck the cold stone floor with a clink as she finally landed.

Her hair looked like an inverted parody of Celestia's daytime mane, the dark center bordered by a semitransparent strip as it flowed through the air, seemingly not caring for the direction of the wind as it waved around behind her. You quickly found yourself becoming lost in it - unlike Celestia's mane, which apart from its otherworldly glow and impossible flow seemed reasonable, Luna's seemed to go on forever. The more you stared, the more details became apparent to you, from pinpricks of light shining through it, to areas of colour and shape. Luna's mane reflected the night sky itself, and staring into it was like looking into the vast expanse of nothingness above the skies of Equestria, unmarred by clouds or your lack of a telescope. No wonder the legends spoke of Luna's terrifying appearance.

As she turned, her body was illuminated by a sudden bolt of lightning, silhouetting her against the moon as it rose behind her, completing her night. You found yourself cowering slightly behind Celestia, your bravery slipping away as you faced the princess of darkness at the height of her power.

"Lu!" Celestia scolded, shoving you out from behind her, "you know there's no need for such a display in private!"

Luna sighed, lowering her head as she walked into the chamber proper, closing the windows as she went. They were stained glass, and depicted the moon in its various stages, save for the lowest parts which were clear. "I know, sister. Forgive me, I simply wished to practice for when I show our subjects my power once more."

Luna spoke fairly softly, her voice like a chorus of angels. Her mane lowered, though it still continued to flow against an invisible wind, and grew foggier, disguising its depths and making her easier to view.

"I understand, I just wish you wouldn't do so when we had guests," she replied, pointing you out with a wave of her slippered hoof. "I have somebody I'd like you to meet, I think you'll find him quite useful. I thought you could use somebody to help you with whatever you need, so meet-"

Luna interrupted, her voice growing harder and louder as she began to shout. "Sister, you should have told us we were addressing a subject! Furthermore, it is unfitting of position to refer to us as 'Lu' while lesser ears listen!" she said, a curious mixture of her previously beautiful voice and a shout. The chorus of angels had turned to something less beautiful, but nonetheless awe-inspiring, terrifying, and commanding of respect. "We have no need of an exotic pet, as you and your student have taken, and are quite capable of looking after ourselves!"

Celestia visibly winced. She turned to face you, whispering "Could we please have a moment in private?" and motioning back towards the door. You were only too happy to be removed from Princess Luna's sight, and gladly took the opportunity to hide behind a set of huge wooden doors. Celestia closed them shut behind you, muffling their conversation too much for you to make out what they were saying.

Falling back against the door, you relaxed, slowly letting your body calm down. Celestia was probably right, Luna didn't actually mean any harm. Perhaps ponies were just less easy to scare 1000 years ago, or perhaps Luna just didn't care. Either way, you had serious doubts about your ability to fill your post.

"Hey, don't worry about it," the guard advised, appearing seemingly out of nowhere. "She's just like that, she wants us to respect her, but she still wants what's best for the kingdom and the rest of us."

You thanked him for his advice - you didn't catch his name earlier?

"Shadow Shield," he replied, puffing out his chest and standing to attention, "corny, I know, but I didn't choose it. I saw you staring earlier, by the way. No, the wings aren't real, though I can fly on them. The princess likes the look better, apparently. Anyway, just hang in there, you'll get used to her. That's really all I had to say, I'd better get back downstairs."

With that, he faded back into the shadows and you lost track of him. You'd have to get somebody to teach you how to do that one.

Feeling more sure of yourself now, you continued waiting, the muffled conversation dying down a few moments before the door slowly opened once more.

"Please, come." Celestia motioned, inviting you back inside. Luna looked far more sedate than before, her hair barely rippling in the air, and almost completely fogged to the point you couldn't see any deeper. She looked far more approachable, for sure.

"Subject," Luna half-shouted, her tone still controlled and demanding of attention and respect, but no longer terrifying, "we have agreed with our sister's plans, and you shall assist us in our night to night tasks. We trust you are ready to begin?"

You nodded - maybe this wouldn't be so bad. Celestia smiled as she saw the two of you begin to get along, and bid her farewell, retiring to her chambers for a much deserved night's rest. For you, and for Princess Luna, though, the night was only just starting. It couldn't be that bad, could it?