Author's Notes: Whoa! Okay, I knew the last chapter was going to get a response, but man, 19 reviews in 24 hours is amazing! And yes, I know, I left you all on a cliffhanger there. All I can do is apologise and warn you to get used to it, because this is a big story moment, which means cliffhangers everywhere!

And since my usual monologues can no longer work due to the threat of massive plot spoilers, I will not say anything more. Thank you for all the feedback, and for reading, and find out just what will happen next...

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Chapter 42

Panic and Chaos

Everything merged together. Colours, shaped, sounds, even the aching in Starfall's body did not seem to have any localised point of origin...his whole being simply ached. For those few, confused moments, he briefly forgot where he was, and what was going on. He was supposed to be...somewhere...Canterlot...the castle. The Ball! Luna!

Starfall's world snapped back into focus with almost painful speed, finding himself lying on the hard dance floor, up against the edge of the raised stage...obviously having been thrown there by the force of the magical blast. His head thumped painfully...likely the onset of a concussion, and while his whole body hurt, he could not feel any serious injury, just some nasty bumps and bruises.

Another loud explosion made him jump to his hooves as quickly as his disorientation allowed him, looking around hurriedly. While he had been dazed and out of action, several more magical blasts had obvious been thrown around, several small craters dotting the dance floor, which was now almost completely devoid of ponies as they scattered, fleeing every which way. Some ran off towards the garden, mostly pegusi looking for a fly to fly to safety. But the vast majority fled for the main entrance, even if Starfall knew it was useless. Starfall knew from his vision that the main door was magically sealed, and it would foolish of the ponies crashing this party to leave the open sky above the gardens clear and free as an escape route.

But Starfall stopped, his blood going cold as he saw that, despite the dance floor being mostly clear, some ponies had not escaped the blasts. Many of them were stirring, clearly dazed like he had been...but others were still, some unnaturally so, leaving a sick feeling in Starfall's stomach...his warning vision had surely come too late for some ponies now. He briefly spotted Twilight off to one side, lying still and silent, her friends crowded around her desperately. But judging by the relative calm most of them displayed, the lavender unicorn seemed to be alive, but hurt.

Starfall saw no sign of Princess Cadance, Shining Armor, or Princess Celestia...as far as Starfall could remember, none of them had been in the room when the blasts had started...there was every chance none of them were even aware anything was wrong yet.

Starfall's attention was focused on another figure, though...Princess Luna. She had been right next to him, and right next to the first explosion. Starfall's horror only increased as he recalled that Luna's position had shielded him from the blast slightly, meaning she had taken the brunt of the impact. She was lying out in the middle of the room, and Starfall had not seen any movement from her.

His panic was only held at bay by the fact that he could see her ethereal mane and tail were still billowing faintly...she had to be alive if that was the case. But the fact that she had not moved was telling...the explosion had hurt her, and Starfall had no idea how badly.

"Luna!" without even thinking about what he was doing, Starfall leapt after her, seeking to at least find a way of getting her to a more sheltered spot, to check how badly she was hurt. He barely made two strides, however, when he felt something strike his side with a stinging, hard force, making him yell out in pain and surprise as he was thrown off his hooves, crashing down to the floor once more, groaning out of both pain, and exasperation at his own stupidity.

Before he could do anything further, however, he heard a triumphant, satisfied laughter...one he recognised, just as he recognised the voice when it spoke. "Well, well, well...isn't this a pleasant surprise!"

Starfall turned to look over towards the source of the voice, up on the balcony surrounding the dance floor. Sure enough, there he was...flanked by a few rough-looking Earth Ponies, who seemed to be keeping an eye out for any Royal Guards inside the castle that had not been subdued yet. The unicorn's black coat, faded grey and pale blue mane, and steely grey eyes were unmistakable.

"Cosmo?" Starfall asked, baffled. Even after the visions showing Cosmo being behind the mess that was to come, he still could not quite believe it. But seeing him here, now, his horn glowing with a silver aura, obviously powering the barriers keeping everypony trapped, Starfall was finally starting to accept the truth against his own will. Cosmo was crashing the party, and clearly had sinister intentions.

"Surprised to see me, Starfall?" Cosmo asked, smirking down at the yellow pegasus, clearly confident. "Thought you could get an invite to the biggest event of the year, and leave me out of it, huh? I thought we were friends?" he asked, the last question being posed in a fake, sickeningly sweet tone, clearly mocking.

Starfall, however, didn't take it as much of a joke as he got back to his hooves hesitantly, his eyes on Cosmo, in case the unicorn decided to lash out at him again. "We were, Cosmo..." he replied softly, almost to himself. "Have you gone completely mad, Cosmo? Look what you're doing, what you've already done!" he yelled, gesturing to the scattered ponies lying about, some of which were starting to stagger to their hooves, joining the rest in the rush for the non-existent exit, while other still lay deathly still...never to get back up again.

Cosmo, however, seemed surprisingly undisturbed by all this, waving a hoof dismissively. "An unfortunate necessity of what has to happen here, tonight," he said idly, Starfall left gobsmacked. He knew Cosmo could hold a grudge, but this new cold, calculating ruthlessness...this was nothing like Starfall could have ever expected from his once-friend. It was not like him at all, even in his crueller moods. Cosmo simply was not a killer...or at least, that was the Cosmo Starfall remembered...

"I told you, Starfall," Cosmo snarled. "I told you karma would come back to get you, and all those responsible for it! Justice will be served, and now it will be served tonight...right here, right now!"

Starfall could not find any words to say...what could he say? His old friend was still holding a grudge from the destruction of Stratos Crossing, that over the last four years, seemed to have turned from a boiling hatred, into an uncontrollable desire for revenge. It was something so horrific, Starfall could never have seen it coming, especially from somepony he had once considered a friend.

Finally, Starfall managed to get his mouth moving again. "Why, Cosmo? Why here, why now? You've had plenty of chances to get me before, so why strike in a heavily guarded area, where somepony is bound to stop you eventually?" As he said this, he spared a glance towards Luna, noticing her stir, ever so slightly. If he could just keep Cosmo distracted long enough...

Cosmo snorted at Starfall's words, half-amused, half-annoyed. "Once again, Starfall, your thoughts go straight to your own pathetic hide. Sure, you're the main focus of my revenge...but you're not the only one I'm after...if you were, I would have dealt with you weeks ago."

As he spoke, Luna started unsteadily getting back up, Starfall taking his chances and rushing over to her as Cosmo turned his attention on her. "Luna!" he called, quickly reaching her side, though she still seemed dazed. If she heard him, she had not understood what he was saying, judging by her lack of answer. "Luna, are you okay? Say something!"

"Ah, Princess Luna...Guardian of the Night...how nice to finally meet you face to face," Cosmo drawled, putting a hideously fake air of formal politeness. "Princess...bah, a mere title. A false display of false power, but then again, Luna...you know what true power is, don't you?" he said, a smirk starting to settle on his features as Luna seemed to begin to come to her senses.

"What wouldst thou know of power?" Luna demanded back, her own horn starting to glow with a pale blue aura, Starfall suddenly feeling a lot safer. Luna was okay...and with her alicorn powers, Cosmo would soon be detained, and this whole mess would be over. "Thou art a coward, striking from the shadows while everypony's back is turned. That is not power."

Surprisingly for Starfall, Cosmo seemed relatively unimpressed by Luna's anger and aggression...something else was not adding up, Cosmo must have some kind of edge neither Starfall nor Luna were aware of.

"That depends on your point of view, Luna," Cosmo quipped back, his horn flaring a little brighter...seemingly attempting some other magic on top of maintaining the force field. "But I do not care for your opinion of my tactics. This, however, I believe is a power you are familiar with," he finally said, levitating a small object in front of him, holding it up with his magic for Luna, and Starfall, to see.

Starfall blinked in confusion, not really sure what he was supposed to be looking at, at first. It seemed to be a small gemstone, round in shape, and a deep purple colour, bordering on black. The gem could easily fit onto the base of Starfall's hoof, and seemed to be little more than a pretty trinket.

Luna, however, had a much more noticeable reaction, gasping and actually moving back a couple of paces, her eyes wide...almost as if she was terrified of being in the same room as the gemstone. "No! That...how did that come to be in thy possession?" she demanded, her voice full of anger. But for the first time since Starfall had met her, the Princess of the Night sounded genuinely scared.

Starfall looked back at the gem, only now spotting a little detail that made him stop and pause. The gem seemed to be swirling and rippling...as if it's core wasn't solid. Now he understood...the gem was some kind of magical object. If Luna's reaction was anything to go by, it was likely pulsing with dark, sinister magic...very powerful magic.

Cosmo smirked, seeming to enjoy Luna's near-panic at the sight of the gem. "Pretty little thing, isn't it?" he asked, twirling it around him a couple of times with his magic. "How it came to be in my possession is not really anypony's concern. What's important is that it has given me the power to put my plan into motion. But even with all this power, I admit I may need some help...help that you will provide, Princess," he said, his tone calm, falsely sweet the whole time.

Luna, however, got over her initial shock and fear. "Never! We swore to never touch the darkness again!" she cried, her horn flaring, firing off a beam of potent magical energy in Cosmo's direction, clearly aiming to stop him right there and then.

Cosmo, however, seemed to see the attack coming. He levitated the magical orb in front of him, Luna's magic striking the orb...and dissipating without leaving so much as a scratch on either Cosmo or the orb itself. Starfall gasped, knowing that Luna, as a alicorn, was an exceptionally powerful magician...for that orb to be able to take such energy and act as if it was nothing meant the magic contained within it was something Equestria had never seen before.

"Cosmo, listen to me!" Starfall cried, trying to take advantage of the lull in the sudden bout of violence. He had been able to connect the dots, and figure out that the orb was full of dark magic, and that unicorns in close proximity to it could utilise it's unspeakable power...but not without allowing the darkness to take over their minds. Luna had obviously seen this power before, and Starfall had a sneaking suspicion he knew where.

But now was not the time, Starfall now knew that Cosmo was not causing all this chaos and destruction of his own free will...he had to get the unicorn to snap out of it, before it was too late. "Cosmo, you're not yourself! The gem is controlling you, making you do this! Can't you see that?!" he called, hoping at least that, if he couldn't snap Cosmo out of it, he could buy them a little time...he could not see Twilight or her friends anywhere, and assumed they had raced off to find help. "Can't you see that this is wrong, what you're doing?"

Cosmo, however, merely threw Starfall a vicious, loathing glare. "Wrong?" he scoffed. "This is not wrong, Starfall...I'm putting right a wrong made years ago!" he roared, firing another spell in Starfall's direction. This time, the young pegasus was more alerted, and so managed to stay out of it's way, although he was forced to back off, away from Luna, to avoid it. "I'm fully aware and in control of my own actions, Starfall...I'm simply doing something that needed to be done years ago, something this magic has given me the power to finally do!"

"This is madness, Cosmo!" Starfall cried. "You must realise that you won't get away with this?! You're in Canterlot Castle...you may have subdued the guards for now, but more will come." He knew it was a long shot, but he was hoping that his warning could scare Cosmo into backing down.

As expected, though, it did not work in the slightest, Cosmo shrugging. "I think you will find, Starfall...that I have come prepared for any eventuality," he said dismissively, before turning and smirking at Luna once more. "Now, Luna, I don't remember saying you had a choice in assisting me!" he yelled, his horn flaring. "You are the Princess of the Night...embrace the darkness you so cherish!" he cried, finally unleashing his magic, the dark orb shooting through the air...straight for Luna!

"Luna!" Starfall cried, trying to move forward, though exactly what his intention was even he did not know. In the end, it did not matter...Starfall was too far away from Luna, the orb travelling too fast to be stopped, leaving Starfall able to do nothing but stand and watch in horror.

The orb slammed straight into the collar of Luna's dress, right where the moon symbol was, Luna crying out and rearing back, even as it started to glow with a vivid purple energy. "No! No, not this...anything but this!" Luna cried, clearly distressed and panicked, Starfall's ears pinning back at her pain, helpless to assist...he did not even know how anypony could possibly help, let alone where to begin.

The purple light coming from the orb grew brighter and brighter, Luna's own horn flaring to life as she tried to use her own magic to combat the dark influence. But even as she made the attempt, it was obvious the darkness was already taking hold, her desperate flailing easing off, the bright glow starting to spread around her body, the magnificent dress she was been wearing vanishing...torn away and obliterated in the wake of the powerful magic consuming the Princess of the Night.

Once the glow of sinister magic spread across Luna's whole body, it morphed into a brilliant white colour, bright enough that Starfall had to avert his gaze slightly to avoid being blinded by it. Beneath the glow, however, he could see that Luna was...changing. The magic was transforming her, shaping her into something new.

Luna's hidden form started to grow, becoming taller, more imposing, more intimidating...and more powerful. Her horn extended in length, as if accommodating for a greater magical prowess, while her wings also reshaped slightly, taking on a fuller, more powerful look.

Finally, after what felt like a lifetime to Starfall, the magical glow faded, leaving behind a sight Starfall had never wanted to see in his life. Where Luna had once stood, there was now a tall, imposing mare, possibly even bigger than Princess Celestia. Her coat was a deep black colour, reminding Starfall of the darkest nights, when the stars refused to come out and play. Her mane and tail had changed dramatically, now resembling wisps of gaseous, purple smoke, rippling and swirling from her head and rump, though seemed to have enough cohesion and solidity to form a distinct mane and tail. Her eyes were still the same shade of cyan, but now had slitted, cat-like irises, and held a terrible coldness and hatred within them.

On top of this new physical appearance, the mare was adorned with several pieces of what appeared to be some kind of ceremonial armour, all made of the same shining, pale blue metal. The whole assembly, from the helmet, to the collar-style chest plate, right down the high front horseshoes, was deceptively simple in design, lacking the elaborate engravings most ceremonial pieces used, but the chest plate in particular was made up of a series of curving, moon-like designs, the centre of the chest plate even depicting a white crescent moon, much like Luna's official royal collar had. Cradled in the hollow of the moon, however, was a dark orb...the dark gemstone had embedded itself there, where it could continue corrupting and feeding off its host.

But it was the cutie mark that pained Starfall the most. The dark, purplish blue splotch, with a white crescent moon imprinted over it, was a mark he was all too familiar with, and the only part of the mare that had not changed at all from Princess Luna.

"No...please, not this..." Starfall whispered, trying to deny the sight in front of him, even as the mare gave a low, rolling chuckle, one he also recognised from his nightmares...the one he had been hearing right from the start. "No...Luna..."

The mare was still Luna, but as her chuckling turned into a full-blown cackle, Starfall realised he was staring at a twisted, perverted form of her. This was the Luna that had, according to legend, been consumed by jealousy and hatred, and corrupted into conspiring against Equestria.

The mare in front of Starfall was no longer Princess Luna. Now, he was standing before the iconic mare of Nightmare Night, and the focus of many horror tales and foal's nightmares for the last thousand years.

Nightmare Moon had returned to Equestria.