"Foul creatures! Thou shalt pay for interrupting my slumber!"
Princess Luna had a tendency to fall back into her old style of speech when she got too tired or angry. As the sun started to set, she was quite a bit of both. Blasting two more cockatrices into unconsciousness, the Princess of the Night turned to see the other beasts retreating. Looking towards the setting sun, Luna felt a measure of relief at what it implied. If her sister had enough time to lower it, that meant the rest of the attacking creatures were retreating as well.
Taking to the air, Luna flew towards the castle, surveying the city below her as she went. Sure enough, as the light of day faded more and more of the cockatrices retreated from Canterlot. Seeing her sister on an upper balcony working her magic on the sun, Luna landed next to her. "I'm glad to see you are alright, Sister." As the sun finished setting she added, "Now it is my turn." Suiting word to action, Luna called upon her magic and began to raise the moon.
Letting her own magic fade, Celestia looked to her sister with a smile. "As am I, although I admit that I had some aid with my own foes."
As Luna finished raising the moon, another voice spoke from behind them, "I am just glad to be of assistance, Princess Celestia."
Luna's eye's snapped open in shock, recognizing the voice instantly. It was the voice that had whispered such promises, such temptations to her. The voice that had helped create Nightmare Moon. The voice of one of the few beings she had ever feared.
Time seemed to slow as she turned, taking in the stallion standing there. The grey coat and wild black hair were all the confirmation she needed, and her magic was already launching toward him as she finished turning.
The dark stallion dodged out of the beam's path so smoothly he seemed to slide rather than step, letting the princess' magic demolish the wall behind him. With an amused expression, he said, "I suppose I should be used to that sort of greeting by now."
"I'm sorry, Luna," Celestia said quickly before her sister could attack again. "I should have warned you about Black Knight's... unusual appearance."
"I believe you mean 'my resemblance to a horrifying tyrant'," the stallion suggested, still looking amused. "There is no reason to sugarcoat it, my dear princess. It is simply a situation I shall have to live with."
"Black Knight, is it?" Luna asked, still eyeing him warily. "You seem to be taking being mistaken for a cruel monster rather well."
"It led to me meeting Lady Twilight, so the situation has not been entirely negative," he replied with a shrug. "I take it you are the other alicorn I have heard so much about, Princess Luna?"
"Indeed," the younger princess said, relaxing slightly. Something was still troubling her, though. Narrowing her eyes, she asked, "Then, would you care to explain how you came to learn Dark Magic?"
"You can sense it that easily? I see your reputation was not exaggerated," Black Knight said before explaining. "I have sworn myself to Lady Twilight as her personal knight. As such, I have helped her train her magic and learned a few new spells from her so as to better perform my duties. Being the premier Dark Magic user in all of Equestria, Lady Twilight would be best represented if I helped her in her goal of showing that Dark Magic can be utilized to aid others, as well as causing the harm it has become infamous for."
"I suppose that makes sense," Princess Luna replied, although the suspicion remained in her gaze.
Stepping in to try and defuse the situation, Celestia said, "I met him before he started training with Twilight, Luna, and I couldn't feel even a drop of Dark Magic from him then. As powerful as King Sombra was, do you really think he could have hidden that much Dark Magic?" Seeing her sister shake her head after a moment, Celestia smiled and went on, "Then let us consider that the end of it." Turing to the stallion in question, she added, "Why don't you join us for dinner, Black Knight? Consider thanks for your aid in protecting the city."
"It would be my honor, Princess," he replied.
"Please, just 'Celestia' is fine," the alicorn replied with a smile.
"As you wish... Celestia. Now, if you'll excuse me, before I dine, I would like to visit the barracks," Black Knight replied. "If you don't mind me saying so, their handling of this situation was absolutely abysmal. Having faced many different kinds of foes before, I believe I may be able to better prepare them for defending against tomorrow's assault."
"Any aid you can give the soldiers would be greatly appreciated, Black Knight. I shall send a messenger to find you when the food is ready," Celestia answered.
"My thanks," he said as he left the balcony. Descending to the lower levels of the castle, Sombra had a thoughtful expression. 'Interesting. It seems the younger sister is not as willing to accept my "death" as easily as others have,' he pondered. 'I suppose I should not be surprised given her more personal experience with Dark Magic. Then again, perhaps I can use this. It will require much more finesse than toying with the Crystal Prince, but the rewards could be so much greater...'
Back on the balcony, Luna frowned as she regarded her sister. Celestia was still gazing after the retreating stallion, an expression on her face that her sister would almost call... dreamy. "Sister, are you alright?" Luna asked. "You have been acting a bit strangely."
Turning toward Luna, Celestia simply said, "Whatever do you mean?"
"Hmm, perhaps I was simply imagining it," Luna said cautiously, "but you seemed to behave a bit oddly around him. That Black Knight didn't use any strange magic around you, did he?"
"Well, he was using Dark Magic the entire time we were fighting the cockatrices," Celestia said dryly. Giving her sister a soft smile, she added, "But more than anything, Twilight vouched for him, and I trust her. That's good enough for me."
"And I trust you, Sister," Luna said with a nod. "Very well, I shall try not to let his appearance keep me from giving him a chance."
"...and in addition to resisting physical assaults, the cockatrices are likely to become resistant to magic as the Secretariat Comet draws nearer," Sombra lectured as he paced in front of the captain of the Royal Guard. "If your soldiers try to face them head on, they will be ineffective, at best, and a hindrance to those of us powerful enough to face the beasts, at worst. Have I made my point sufficiently clear?"
"Crystal," the captain replied. Glancing down at the growths of dark crystals holding him in place, he asked, "Speaking of, would you mind? I have to get my troops prepared for tomorrow."
"Hmm? Oh, yes, you may go," Sombra replied, waving a front hoof dismissively as he released the magic he had used to force the officer to listen to his 'advice'. Sombra had to suppress a smirk as the other pony stomped out of the room, clearly angry about what had happened but knowing when he was outmatched.
Leaving the barracks, Sombra finally let the grin spread across his face, only for it to be replaced by a look of surprise as he collided with another pony coming the opposite way. The unicorn mare dropped the package she was carrying as she fell backward from the impact. Reacting swiftly, Sombra caught the package with his magic and shifted it to the side to see her more clearly.
The mare had a white coat and purple-and-white mane, with a cutie mark in the form of a trio of purple stars. Rubbing her horn, she opened her teal eyes, only to freeze as she took in the intimidating stallion in front of her. "Ah! M-My apologies," she stammered. "I-I should have been paying more attention."
Forcing down a more annoyed response, Sombra replied as the 'noble knight', instead. "No harm was done, my lady, and I am just as at fault. I am Black Knight. Might I ask where you were gong in such a rush?"
Relaxing a bit, the mare replied, "I'm Twilight Velvet. My son was the former Captain of the Royal Guard, so I like to help out when I can, like delivering these medical supplies to help the injured soldiers."
Sombra's grin returned in an instant. "I see," he said as he turned back toward the barracks with the package of supplies, "Now I know where Shining Armor and Twilight Sparkle get their helpful dispositions."
"Oh, you know my children?" Velvet asked, falling into step beside him.
"Shining Armor I have only met briefly but I am quite familiar with your daughter," Sombra answered. "I am almost offended she has yet to mention me."
"Oh, are you perhaps... Twilight's coltfriend?" The mare asked.
Sombra chuckled at that. 'How peaceful Equestria has become, that romance is the first thing on so many ponies minds,' he thought. Aloud, he replied, "No, no, it is a bit more complex than that. Your daughter saved my life and gave me an opportunity despite my... intimidating appearance. As such, I have sworn myself to her as her knight, to serve and protect her."
"Really? Oh, you must have her bring you to our home here in Canterlot for dinner," Velvet said. "Once this whole cockatrice situation has been resolved, of course."
"I would love to," Sombra said with a smile. Stopping in front of the barracks infirmary, he passed her the package as he continued, "Speaking of dinner, I am late for an appointment with the princesses. If you will excuse me, please have a pleasant evening."
"You as well, Black Knight," Twilight Velvet replied. As the stallion left, she could not suppress a giggle as she muttered, "My daughter has her very own knight, and even he gets to dine with royalty. I can hardly wait to rub this in Upper Crust's smug face."
The next day seemed to pass as a blur for Sombra. Fighting the berserk beasts from dawn to dusk, he could sense the magic empowering them growing as each passing hour brought the magical comet closer. By the time the last day dawned, the guards had been relegated to little more than clean-up duty, only the Royal Sisters and Dark Magic-wielding Knight powerful enough to fight the creatures directly. As noon struck, and Sombra found himself without a new foe immediately apparent, he heard a voice in the back of his mind.
'Sombra, can you hear me?' Came the voice of his student.
'Twilight, I was beginning to wonder if something had happened to you,' Sombra replied. 'It would seem I owe you an apology for underestimating you.'
'Well, Chrysalis has been making things difficult, but we've managed to get through it all and are outside her castle now,' Twilight explained before asking, 'How are things in Canterlot?'
'Well, interactions with the Two Sisters have been rather civil and your mother has invited us over for dinner once this is all resolved. Oh, and the giant rampaging cockatrices have provided an excellent excuse to exercise my Dark Magic in public,' Sombra said telepathically, with a dry tone.
'...You're going to have to explain that when we have more time,' Twilight replied. 'Anyway, I just wanted to let you know I had arrived. We know Chrysalis has some sort of trap in place, so I'll need to stay focused on things here until I'm done. I'll make sure to contact you as soon as she's dealt with.'
'Very wise,' came Sombra's response. 'I shall ensure the situation here is under control by the time you return.' Seeing another group of cockatrices approaching, he began to focus his Dark Magic and added, 'Although, I must admit that I never expected to enjoy myself this much while helping others.'