Author's Notes: Once again, the response to my last chapters has been absolutely amazing! A big thank you to everyone who reviewed!

On that note, actually, PepperjackPegasus briefly mentioned another MLP fic, "Past Sins", and a character called Nyx. I'm afraid to say I have not read "Past Sins", and know very little about the character Nyx, except from a few references and pics thanks to my time surfing DeviantArt. From what I can tell, Nyx is Nightmare Moon...only not evil, but since I haven't read the fic, and am not a fan of copying other people's ideas, I can assure everyone that Nyx will not make any sort of appearance in Magic.

As for what WILL happen, well, read on and find out...

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Chapter 43

Sibling Conflict

Starfall could only stare in horror at the mare of darkness standing before him, relishing in the dark power coursing through her. This could not be happening...Luna could not, would not, do this! But this was no bad dream, and Starfall was forced to admit the frightening reality as Cosmo gave sharp laugh, clearly noticing his former friend's horror.

"What's the matter Starfall?" he mocked, clearly enjoying Starfall pain. "She's still the Princess you know and love, you know," he continued, Starfall not even noticing the use of the word 'love', even if Cosmo had not deliberately used it. "I just freed her, unshackled her and let her unlock her true potential," he explained coldly, still chuckling to himself.

"No..." Starfall breathed, still trying to comprehend the hopelessness of the situation. She was Princess Luna, co-ruler of Equestria, Guardian of the Night, and an immortal, powerful alicorn, practically a goddess. How could Cosmo have defeated and turned her so easily? It just did not seem possible.

Even as Starfall was grasping the situation, however, Nightmare Moon turned, taking a look out the massive, tall windows, looking out into the castle gardens, her attention focused on the night sky above them. "Ah, my beautiful night...still ignored and shunned, even after all these centuries..." she muttered, as if to herself, but with cold, hard edge, obviously displeased by what she was saying.

"Not for much longer." Cosmo's reply made both Starfall and Nightmare whirl around to face him. Starfall was rather surprised. First he goes on and on about revenge against the wrongs made to him, and now, he seems to be pandering to Nightmare Moon's quest to plunge Equestria into eternal night.

While Starfall did love the night, and all its hidden wonders, having the sun never rise again was not something he was a fan of...Equestria in eternal darkness would not last very long before the countryside began to wither and die away. A balance of night and day was needed, neither one pushing away the other...and Nightmare Moon was fully intent on upsetting that balance.

Nightmare, however, seemed merely curious about Cosmo. "You have the aura about you, young stallion..." she remarked, relaxing slightly, before pausing, as if deep in thought. "You...you seek revenge on the yellow stallion, and my wretched elder sister," she added, Starfall struggling to keep up.

From what Starfall could tell, since both Cosmo and Nightmare were being corrupted by the same dark orb currently resting on Nightmare's chest, they had some way of sensing each other...able to tell what the intentions of the other one were. The part that scared Starfall was that Nightmare did not seem too troubled by Cosmo's intentions, and actually supported them, if her tone was anything to go by. On the same vein, Cosmo's corruption had clearly seen him become a supporter of Nightmare's quest for everlasting night.

Cosmo nodded. "Things need to change here in Equestria, and tonight is the night to do it," he replied, smiling down at the mare of darkness. "And who better to help me than the mare who very nearly changed Equestria once before. Together, I'm sure we can put an end to the farcical leadership here...and of course, I will support your quest to plunge Equestria into everlasting night. Unlike Starfall here, who calls himself a lover of the night sky, I wish to see ponies embrace the night, whether they want to or not."

Starfall literally could not believe what was happening right in front of him. His former friend, and oldest acquaintance, and the corrupted form of the mare who had claimed his heart, were conspiring to tear Equestria apart, with little concern for anypony that got in their way. "No..." he pleaded, looking between Cosmo and Nightmare, trying to find something, anything in either of them that said they did not want to do this, that they could be convinced that what they were doing was wrong. "Please, can't you see what you're doing? You're going to kill thousands of ponies!"

Cosmo, however, merely snorted. "I already explained this to you, Starfall, so do us all a favour and keep your worthless protests to yourself!" he yelled, before pausing, raising a hoof as Nightmare's horn glowed a vivid, deep blue, making her pause. "Leave him, Nightmare...he's harmless. A worthless, weak coward who wouldn't even risk his own neck for the ones he would call friends. I want him to witness this...to let his last moments be made standing and watching from the front row as the Equestria he knows falls, never to see the new future that will be born of the ashes of this unfortunately necessary destruction. I trust you have a method for what I intend?" he asked.

Nightmare looked at Starfall for a few long moments, as if assessing the young stallion's potential threat to her, and to their plan. Starfall managed to muster up the courage to look at his corrupted, secret love, trying to find some sign, any little signal that said the Luna he knew and loved was still in there. Those slitted eyes, however, held nothing but darkness and shadow...a fierce, all-consuming desire to take over the spotlight, by any means necessary.

But, for a split-second, Starfall thought he saw something...some faint glimmer of recognition in those eyes, as if the old Luna recognised him, just for a moment. It was gone before Starfall could confirm it, however, Nightmare turning back to Cosmo. "Of course I do," she said, before turning to make her way to the castle gardens...clearly whatever the plan was required access to the night sky.

For a brief moment, Starfall wanted to stop them, even taking a half-step in Nightmare's direction, before pausing. Exactly what could he do? Cosmo, as much as it hurt to admit it, had a point. He did not know how to fight, and was not a good flier. More to the point, as a pegasus, he was a very easy target for either Cosmo or Nightmare's magic attacks. A sense of uselessness fell over him as his whole body seemed to sag...he just had no way of stopping them.

But before Nightmare could make it into the gardens, a golden glow surrounded the doors leading out to the dim woods, slamming them shut forcefully, just as a harsh, but familiar voice rang out. "Halt! You will go no further!"

Starfall whirled around, cringing even as relief flooded his being. There, standing at the door to the entrance hall, was Princess Celestia, the appearance of Twilight and her friends telling Starfall who had alerted the elder Princess to the danger unfolding. The Princess of the Sun looked absolutely furious, eyes narrowed, but at the same time, her gaze held a certain pain to it, one Starfall did not take long to figure out. Even if she was intervening on a threat against Canterlot, Nightmare was still, in a twisted way, her little sister, and the regal Princess was obviously reluctant to hurt her family.

Nightmare Moon also whirled around, smirking at her sister. "Well well well, my sister is late to the party, as usual. I am afraid times have changed, however...you will not stop me this time, Celestia. The Elements of Harmony have abandoned you, and without the aid of their power, you cannot stop me!"

Starfall paused, blinking. What did Nightmare mean? The legends had always stated that Celestia had banished Nightmare Moon a thousand years ago by harnessing the power of the mythical Elements of Harmony. Starfall had never really believed it, but Nightmare seemed very sure of herself, and Princess Celestia was making no attempt to deny the dark mare's words.

The sudden sound of spell fire interrupted the conversation, however, Starfall turning around again, to find Cosmo suddenly raining spells down on Twilight, who was firing spell after spell at the twisted stallion...her brilliant magenta magic looking impressively powerful. The rest of her group were also making an effort, though they seemed to be distracted by Cosmo's Earth Pony bodyguards, who clearly knew how to fight.

Princess Celestia looked at the scene for only a moment, before turning back to Nightmare Moon. "Nightmare Moon...do not do this. I know the real Luna is buried in there somewhere...and I know she would not do this. I do not want to hurt you, but I will stop you if I must." The conflict in her voice was clear, the pain at was she was threatening obvious. The Princess was in a terrible situation, forced to confront her own sister, who she clearly loved.

Nightmare Moon, however, did not have such a conflict troubling her at all...Celestia's pain only seemed to amuse her. "What's the matter, Celestia? Conflicted? Reluctant to stop me? If you do not wish to hurt me, then why bother stopping me? You'll only see yourself hurt, anyway," she taunted, her voice cold, malicious...all trace of sisterly affection Princess Luna may have had was simply gone, lost to the corrupting influence of the dark magic coursing through her.

Princess Celestia, however, did not seem to be willing to back down. "I will stop you, Nightmare Moon, because the shade I see before me is not my sister, even if you take her body and pervert it for your own ends. And I will stop you, because I look after much more than my own personal feelings. The freedom and liberty of all of Equestria rests on my shoulders, and I will protect these virtues...even from you." The pain and reluctance were still there, proving the Princess did not want to do this if she could help it...but there was also a fire in her eyes, a determination...she would protect Equestria, and protect it with her life, if need be.

Nightmare Moon, however, simply laughed. "Ha! Your words are brave, yet you still refuse to cast the first spell, sister. You don't have the guts to strike me down unless it is to defend yourself. You cannot bring yourself to attack me, you never could!" The smirk on her face was amused and confident...if the Elements of Harmony existed, and Nightmare's words about them true, then the mare of darkness had all the advantages. Despite being the younger sister, the dark magic flowing through her would likely make her power equal to, if not surpassing Celestia's. And while the elder sister was conflicted and torn, Nightmare had no such inhibitions.

"It's a cruel irony, isn't it? Because you were the eldest, you became the primary ruler of Equestria, Guardian of the Day and Princess of the Sun. Everypony loved you, cherished you, while I was shunned and ignored, along with the beautiful darkness of the night I had worked so hard to create for their pleasure." Nightmare's words were turning foul and bitter, practically growling, as if she was on the very edge of lashing out violently at Celestia, of ending the verbal debate and just settling this through raw violence.

But her calm smirk reappeared once again. "But in the end, everypony has been seeing a false illusion. You Celestia, are a coward. Of the two of us, which sought true power, while the other held back, harping on about the magic of friendship and love? Which of us is willing to do whatever it takes to get the job done, while the other holds herself back for fear of slighting or scaring every last thing in this land? Which of us would have snared ultimate victory, seized ultimate power, were it not for those worthless stones you swear by every other day?" She practically spat the last one, glaring at her sister, eyes full of cold hatred, malice...and jealousy.

This, Starfall realised, was the core of the issue...the dark magic was feeding off of Luna's jealousy towards her sister, and anger at the way ponies ignored her beautiful night. It fed on that, making those emotions consume her, turning her into the mare of darkness currently ranting at her sister. In the same context, the magic must also be doing something similar to Cosmo, feeding off his anger and thirst for revenge, and making him act out that desire. Cosmo's physical appearance had not been altered like Nightmare...likely because of Luna's status as an alicorn...but the psychological changes were impossible to deny, the dark magic had turned Cosmo into an evil lunatic. Devoid of any fighting ability, all Starfall could do was watch, and pray that both Cosmo and Nightmare were stopped, and brought out of the darkness influencing their minds, before his vision could turn into reality.

Princess Celestia, however, seemed to take offence to Nightmare's remark, giving the dark mare a seething, harsh glare, clearly unhappy. "You call me a coward? I have only ever sought to use my power to help all Equestrians, be they Earth Pony, Pegasus, Unicorn, or even Alicorn, make a better life for themselves. You, Nightmare Moon, seek power for infamy and glory, and refuse to share it. You, Nightmare Moon, are so afraid of being lost to the shadows you adore so much, that you would plunge all of Equestria into permanent darkness, just so you don't feel so alone. I tried, my sister...I have tried so hard to show you how much I love you, and that if you would just give them a chance, how much the ponies we watch over would love you..."

"Enough!" Nightmare Moon's sudden yell startled Starfall, making him jump and take a few paces back, worried the mare of darkness was about to start firing spells. While it was clear Celestia's word had done little more than enrage her, she somehow still manage to control her desire to just blindly attack everything in sight. "Enough of your lies, sister! We heard it all last time, and I never believed you, then, either! Since you refuse to leave me be...I am left with no choice..."

Starfall paled as he realised what was about to happen. This night just kept going from one horrific event to another. Nightmare Moon was not going to be swayed, the darkness was too set within her, making her too focused on the destruction she intended to cause for any form of argument to entice her back to good.

According to the legend, the last time Nightmare Moon was defeated, it had only occurred because Princess Celestia had harnessed the powers of the Elements of Harmony...but Nightmare had said that the Princess could no longer control their power, and with the tale being nothing more than a legend...one that Starfall had not even considered believing until now...there was no way for him to know what had happened to the Elements, and who could possibly control them now.

Which meant that this time, Nightmare Moon's only known weakness was not present and available for them to use to stop her, meaning that Equestria's hope lay solely on the shoulders of Princess Celestia now. Twilight and her friends were still busy trying to subdue Cosmo, and as far as Starfall could tell, that was a struggle that was going to last some time.

But, even as Nightmare's horn glowed with that dark blue aura, ready to challenge Princess Celestia in what was sure to be one of the most powerful and violent displays of magic in Equestria's history, Starfall paled as he realised something he had overlooked during the whole debate and confrontation. He was positioned between Nightmare Moon and Princess Celestia...right in the magical crossfire!

As Starfall's mind processed this fact, his body freezing up in panic as Nightmare Moon prepared to fire her first blast, somepony else realised Starfall was in danger, as he suddenly noticed a golden aura surround his body...Princess Celestia! She was risking herself, leaving herself open to attack whilst trying to get him to safety!

"Wait!" he cried, trying to stop Celestia...if this distraction caused her to get injured...or worse...Starfall knew it would all be on his hide if it came to that. Equestria's fate hung in the balance at this very moment, and the Princess was still more worried about getting him to safety?

But wither Celestia did not hear his protest, or simply ignored, the magic levitating him into the air and hurriedly hurling him across the room. The young pegasus slammed into the ground rather hard, rolling several times until he ended up on his stomach, vaguely spotting through his dizzy, spinning vision that he was near the door to the entrance hall, where he could still hear the desperate cries of dozens of ponies trying to escape the sealed castle.

Starfall rolled back around to face the main lobby floor...just in time to see Nightmare Moon fire off her first spell, the pulse of deep blue magic shooting across the room at the elder Princess, who was still focused with the aftermath of the spell that had pushed Starfall aside, and as such was unable to block or retaliate.

But just as Starfall feared the Princess was going to be struck down before any sort of resistance could even be formed, she moved with a slick agility Starfall had never seen before, twisting out of the way of the incoming spell, which shot passed her, slamming into the wall behind her and exploding violently, showers of marble and dust raining down behind the Princess.

Celestia ignored it, even when some small shards rained on her back, too small to do any damage beyond dirtying her snow white fur, her eyes narrowing as, with the centre of the room now clear, she could focus her efforts solely on Nightmare Moon, her own horn glowing a brilliant gold as Nightmare also prepared her next spell, both of them glaring at each other with steely, determined eyes. Neither one was going to back down without giving it everything they had.

And as Starfall slowly got back to his hooves, both Princesses fired off their spells simultaneously. The battle for the fate of Canterlot, and by extension off of Equestria, had now well and truly begun.