With a snap they were at the gates of Canterlot. The city looked terrible, Gloom's magic covered every street in shadowy tar-like gunk and the agonized cries of ponies could be heard as tainted rain fell. The air itself smelled of sorrow, pain, and rot. Discord looked at his claw, puzzled.
"Odd, I wanted to drop us off at the palace, not all the way at the gate." Discord snapped again and his claw flashed with magic, but it quickly flickered and went out with an undignified farting noise. "Hmm, maybe my other claw?" Discord tried again but no luck, he even tried snapping his tail but got the same result. "Oh c'mon, I know my magic is fine, see?" Discord snapped his claw again and suddenly his thinking tree appeared, he sent it away with another snap.
"Wait, let me try something," Twilight said. Her horn glowed and she vanished in a purple flash, only to reappear exactly where she was. "I can't teleport anywhere past the gate!"
"That meanie pants monster must have put more meanie magic here than in Ponyville," Pinkie frowned.
"This looks like a job for awesomeness!" Rainbow said with a smile, "I'll just fly over to the palace really quick and see if Celestia's okay." Rainbow shot through the air with a burst of color and a sonic boom. The instant she flew over the wall, the clouds of dark magic whirled to intercept her. "Oh my GOSH!" Rainbow yelled as her path was suddenly blocked by huge, angry looking clouds that attempted to seize her. Rainbow pulled a hard 180 degree turn and a burst of speed to outrun the unexpected attack and arrive safely back to her friends. "Never-mind, looks like that monster made it a no-fly zone."
"Look's like we're hoofin it," Applejack stated. The 7 ponies, dragon, and chaos spirit entered Canterlot and started making their way through the cursed streets. The dark magic didn't seem to be as strong closer to the ground although some dark tendrils and clouds did attempt to seize the small group. Discord, Twilight, and Sunset were able to ward off the minor attacks with basic shield and ward spells. Overall, the shadow over Canterlot was more passive than the one over Ponyville, since it wasn't directly guided by Gloom. The band simply avoided the rivers of liquid shadow and moved where the black smog was thinnest.
"Hey Discord, why don't you fly to the palace? I'm sure you could make it through those clouds," Rainbow asked.
"Oh, this is embarrassing, I'm not actually a great flyer. My basic flight skills would never get me by those obstacles. I guess I could try to shield myself and power through, but chaos shields are more for quick blocks, not sustained barriers meant to last hours or even minutes. I can do an instant burst of supersonic speed for a second or two, but my control flies out the window and I'd rather not slam face first into a cloud of Gloomy's dark magic."
"Wow, that means I'm a better flyer than even Discord," Rainbow smiled.
"I never practice flying, why bother if I can usually just teleport everywhere," Discord rolled his eyes.
"Why do you call the creature that nickname?" Rarity asked.
"Cause it really irritates him and takes away from that whole wannabe ultimate evil thing he puts on."
As they made there way through the cursed streets a faint rumbling could be heard in the distance, getting louder and louder. The group turned in the direction of the noise coming from somewhere outside the city. At first they could see nothing, but then on the horizon and shadow seemed to rise and advance towards Canterlot at alarming speed. The ponies expressions turned from puzzlement to surprise to horror while Discord's face became very grave. As the shadow grew closer it was revealed to be a huge army of phantom ponies charging at full sprint towards the city gate. The ponies were literally made of shadows and had no features besides their silhouettes and all were screaming madly as they stormed the city gate. They ran as if possessed, their legs not galloping as ponies do, but jerking and twitching in a spastic skittering motion. They climbed over walls and up buildings with disturbing similarities to insects.
"What in the hay are those!" Applejack yelled.
"Zombie ponies? Shadow ponies? Possessed ponies? Super changelings?" Pinkie started guessing.
"Nightmares," Rarity said, her voice barely audible, "I'd recognize them anywhere after..." Rarity winced as did her friends as they recalled her brief reign as Nightmare Queen.
"What horror has Gloomy unleashed? Run! Run!" Discord yelled. The group fled towards the palace as the horde of shadow ponies reached the gate. The horde quickly gained on the band of heroes as they frantically tried to escape. Discord stopped and spun around to face the oncoming shadows. "Keep going! I'll distract them." Fluttershy paused for an instant, not sure whether to leave Discord. "I'll be fine, these shadows got nothing on chaos," Discord spoke softly to her but there was a wicked gleam in his eyes and a crazed smile on his face as he stood before the oncoming nightmares. Fluttershy nodded and galloped away. A pogo stick materialized under Discord and he bounced straight into the crowd of enemies. "Hey you mindless mooks!" The horde stopped and surrounded Discord, hissing, snarling, and wailing, but seemingly hesitant to actually attack him. One very brave or very stupid nightmare tried to bite Discord from behind. Discord scooped it up with his tail and examined it. "Ah! So you are golems made from Gloomy's magic and granted consciousness through possession. Wonderful, that means you aren't really alive, so I can take the chaos up to 11! It's so rare that I get to cut loose nowadays, Flutters would never forgive me if I did permanent damage to anything, but we can all keep this between us right?" Discord's eyes had a mad gleam. Some of the nightmares started backing away, a few others tried to circle around Discord to chase after the ponies. Discord snapped his claw and a wall of peanut brittle appeared blocking the nightmares' path. "No," Discord stated, his voice completely flat and devoid of the usual playfulness, which somehow made it even scarier. The nightmares were caught between their instinctive fears of two different greater spirits. They froze, not sure what to do. Then Gloom's irresistible command repeated itself in their rudimentary minds. Spurred to the point of frenzy, hundreds of them leaped at Discord with wild abandon.
A few blocks away the ponies charged through the streets. Fluttershy kept looking back.
"Do you think Discord will be alright?" she asked her companions. Suddenly a massive cacophony erupted from the direction they had left Discord in. It didn't even sound like anything, just noise. Looking back the ponies saw what could only be described as a tear in reality, but that was a poor attempt to describe the indescribable. Space and time warped defying all logic in a sort of bubble of chaos that could drive one mad if they peered too deeply. Discord's laughter could be heard along with the shrieks of the nightmares. The sight was truly fearsome, but the ponies couldn't look away simply because their minds were trying to process what they were seeing. The only reason they didn't stare, transfixed was because they also noticed still more nightmares entering Canterlot from the western gate on the other side and heading in their direction.
"I think he's got this, we better move before more of those things catch up with us," Twilight finally said. They raced towards the palace as the nightmares gave chase. The rushed through the courtyard and into the main hall. Twilight seized the large doors and slammed them shut with her magic, she then barred them with the strongest warding spell she could cast quickly. The nightmares slammed into the door and it creaked and groaned under the force of their bodies, but it held.
Outside the nightmares battered the door in a frenzy, unable to reach their targets. A single shadow pony stood apart from the others, staring at the sealed door. This is not a nightmare, despite sharing their appearance and binding to Gloom; it is far worse. It is said that the dreamworld is impossibly vast, the part that is visited by ponies as they sleep is merely the surface. Beings such as Luna can probe deeper but are still limited to the part nearest to the real world. The deepest parts of the dreamscape are not the figments of ponies imaginations, but they are another plane of existence entirely, one that all worlds are simultaneously connected to and barred from. There are things that live in the dark, things that want out. Unbeknownst to Gloom, when he momentarily weakened the barrier between worlds to let the nightmares through, he also allowed something else to slip through. Seizing the opportunity, the thing entered one of the bodies Gloom made for the nightmares and pretended to be one. Gloom's command to all the nightmares was easy for it to shake off, its mind was its own. It was weak, restricted by the body it was in, it needed more or it would soon die like a fish out of water. As it moved among the swarm of nightmares, it searched with its mind for a suitable host. Discord was too powerful and worse would recognize the thing for what it was, the 7 ponies and dragon were tempting but risky especially since they were in a group. The ponies scattered throughout Canterlot were weak and under Gloom's control, trying to seize any of them would attract Gloom's attention and expose the thing's mind to Gloom, not worth the risk. This thing was a predator and knew to avoid the claims of another predator. However, there was one other consciousness in the palace that was free of Gloom, but at the same time too weak to fight back. The thing left the crowd of nightmares and trotted around the palace, looking for another entrance. It found one near the back end, a destroyed balcony that had been overlooking a garden. It was easy to scale the wall and enter Celestia's chambers and even easier to follow the trail to where Gloom had stored the fallen princess.
Celestia had freed herself from the pool of shadow that had been her prison. It had taken tremendous effort and will, but she at last was free. Not that it mattered, she mused. She couldn't summon the strength to stand, and had only been able to drag her crippled body a few meters away from the pool. She only had a tiny spark of magic left, not enough to do anything with. Celestia sighed in defeat, once again it was up to the bearers of harmony to pull her flank out of the fire, once again she had failed in her duty, but it was pointless to despair over that which she could not affect. Perhaps if she simply lay there and focused on recovering her strength she would eventually be able to be of some use. Celestia began meditating, gathering and building her magic, it was working, but agonizingly slowly. Her thoughts were interrupted as she felt a presence enter the room. Her eyes snapped open and she saw what looked like a pony made of shadows. At first she thought Gloom had come back for her, but as the thing neared it was apparent that it was not Gloom, although it was made of similar magic.
"Great! So what are you now? Come for my power or knowledge? Well you are little late, I was just bested by one usurper and unless you're here to simply kill me I have nothing left for you to take. So kill me, help me, or just sit there and stare, I honestly don't care anymore."
The thing didn't answer, it slowly walked up to Celestia and leaned close to her face, never once blinking as it stared at her.
"Don't bother with mind magic, I know how to guard my thoughts and I've been doing it for a thousand years."
But the thing didn't touch her mind, instead it reached down and grabbed her muzzle. Celestia found her mouth instantly pried open and the thing started trying to enter. Celestia tried to scream but her mouth was plugged by the thing's hoof. It started compressing itself, contorting its body to fit more of itself into Celestia's mouth and down her throat. The thing was now completely inside her and had slithered down her throat. She contorted and twitched in a terrible seizure and unimaginable pain, then all at once the pain ceased. Celestia was so relieved that the pain had gone that she tried to sigh in relief, only to find that her lungs didn't exhale and her mouth did not open. She then felt herself stand up and the pain of her injuries ripped through her. She started walking, her body ignoring the pain, unable to even make a sound. It felt as if her body was a puppet, she walked like one too, in jerking, clumsy motions. She still felt every movement but could only watch as though it were through somepony else's eyes. She felt the thing try to cast a spell with her magic, then her body staggered as the spell failed. Her possessor then cast the spell with its own magic, healing some of her injuries. The thing had left her mind alone as it hijacked her nervous system and motor functions so she had no contact or communication with this mysterious creature. She could feel it moving inside her body, just under her skin, if she could move of her own accord she would shudder and probably vomit. The only indication of her sorry state other than her unnatural movements was that she had broken out in a cold sweat and her eyes were frozen in a look of pure fear.