From the blackness ahead of them, just out of the light pouring from Celestia's horn, the growls the two mares heard were followed by a series of heavy thuds crunching against the tunnel floor. There was no mistaking that they were footsteps nor of whom they belonged to. Celestia and Twilight looked up as the monstrosity came into view. Despite the Princess being unphased, the unicorn held her breath and shrank into herself.

"H-Hey Cerberus," Twilight mumbled as cordially as she could. "Uh.. long time, no see!"

The only response she received was more intense growling. Tendrils of thick saliva dripped from the sides of his three mouths and splattered onto the rocks at his feet. The massive dog's breath had a foul smell of decay behind it, causing Twilight to fight off retching right in front of him. It was a bit of a struggle, but she managed not to empty her stomach, fearing it could possibly offend the guardian and invite his wrath.

"I don't understand, Princess," she whispered after composing herself. "He knows me. Why is he acting like this?"

Not taking her eyes off Cerberus, Celestia replied, "I heard about when he got loose and you escorted him back here. For that, I have no doubt that he was grateful. But now, we're intruders. Nopony would normally actively seek this place out, and I know you know why he's here."

"Yes. He guards the gates of Tartarus to make sure nothing gets in or out."

"And that's precisely why we're here." The princess took a step forward and addressed the large three-headed dog. "It seems you, and this foul place's ruler, have been having some difficulty keeping the spirit of a certain pink pony in check, Cerberus. Quite an embarrassing predicament. I intend to find out why, but I also intend to find a way to stop her. You know the answers are behind that door. Let us in."

The large canine remained in place and growled loudly at the Princess' request. He slowly began to sway his shoulders back and forth threateningly, as if telling the mares he was intent on striking if they didn't leave this place.

Undaunted, Celestia squinted angrily and scratched at the ground. "You know what I'm capable of, Cerberus. Don't make this difficult."

The hellhound snorted and stared back at the Princess. Their growls subsided slightly but still rumbled in the back of their throats. The middle head suddenly snapped in Celestia's direction, spraying a few strings of drool into the air. Twilight jumped back as one of the blobs narrowly missed landing on her. The alicorn stood her ground and puffed out her wings, showing no signs of fear.

When she refused to move, Cerberus became agitated. The middle head pursed his lips and muttered a quiet, bothered grunt. His right head snapped at him, furious that he could be vexed so easily. The other two heads snarled back and the initial aggressor pulled back defensively, his ears prone and his teeth bared. Once the scuffle ended, the three turned their attention back to the unmoving mare. She remained as calm and stoic as a statue in her royal gardens.

With a less than intimidating bark, Cerberus took a slow step backward, and then another. Eventually, he stepped to the side of the tunnel and allowed them passage. Celestia cautiously folded in her wings, keeping a watchful eye on the beast. He sat down and briefly licked his right forelimb with his right head, fighting off a sudden itch. The other two were relatively relaxed by now as well; their growling and bravado was no longer a concern for the two mares. Still, their eyes never left the passing ponies and readied themselves for any possible altercation.

"Come, Twilight. It's just a few more feet now. Once we're inside, let me do the talking, and stay close," the Princess whispered. Despite the softness of her voice, it carried throughout the cavern surprisingly loud. The young unicorn nodded nervously.

The alicorn resumed her march down the dark tunnel with Twilight huddled up beside her. They walked about another minute forward when they came into an enormous, open area. The tunnel they followed was already quite large; Cerberus was able to stand on his hind legs with plenty of room overhead still if he so desired. The sprawling room before them utterly dwarfed the size of the corridor before it.

The glow that radiated from Celestia's horn lit brighter and revealed several meters ahead, at the far end of the room, two massive stone rectangles directly beside each other, easily twenty feet tall and fifteen feet wide from one side to the other. Despite the room having been undisturbed for as long as it had been, there were little to no signs of aging or deterioration.

Twilight gasped at the sight. She had brought Cerberus back to his cave once before in the past. She never bothered to venture farther ahead. There was no reason to once the guardian was returned. Seeing the enormous wall with what must have been the gate to the underworld made her wish she had. It was one of the most fascinating, and yet terrifying, things she had ever seen in her short life.

"We're going in there, aren't we?" the unicorn asked.

"I'm afraid so. We must get to the bottom of this. For whatever reason, Pinkie's spirit is being allowed to run rampant. Even after everything that's happened, I simply can't believe she's done what she has. She was one of your dearest friends, and the most easygoing ponies you could ever know! There has to be an explanation for all this," Celestia said grimly.

"I hope we can find one." Twilight looked at the enormous doorway in front of them and breathed deeply. Her sudden nervousness twisted her stomach in knots. "S-So, how do we get inside?"

"Leave that to me." Celestia took two steps forward, a look of deceptive determination in her eyes. She would never admit it, but she too was feeling uneasy about entering such a place again.

Twilight's ears stood at attention and she blinked hard. "You know how to open the door? How? Why would you know something like that?"

"Once we are done here with this place, I will explain everything. Though, I.. don't like to talk about it. Too many memories I wish I could forget," Celestia whispered as she hung her head. After a moment of quiet reminiscence, she returned her focus to the stone doors.

She cleared her throat and breathed deeply. The Princess began to speak in a dialect not heard for thousands of years. As she did, the glow from her horn intensified.

"Khul'aba m'nishtu xel gajika'necht. Ostyrioj ub niqiroloh vas. Y jeirdu tahz'vudahm!"

At the end of the incantation, several ancient, unintelligible symbols and hieroglyphics appeared across the doors, glowing shades of fiery orange and red. The colors almost appeared to be alive, pulsing and shifting about. A low hum filled their ears and the world around them began to shake slightly. Suddenly, the doors began to open inward, slowly, grinding against the floor inside. From within, a bright light peeked around the frames of the doors before illuminating the entire room, causing the mares to shield their eyes.

Once the blinding light subsided, Twilight and Celestia looked ahead into the unknown. The unicorn felt a shiver go up her spine as her mentor took the lead and walked inside. A step behind, she followed. Once they cleared the double doors, Celestia turned around and repeated the spell, shutting the gate with a loud, echoing boom.

The Princess took a deep breath and resumed her trek into the heart of the hellish world. Twilight's eyes raced back and forth as they walked, taking in every detail around them.

Jagged rock formations lined the sides of the path they traveled on. Off to the sides, jets of flame burst from the cavernous pits below and dissipated in the air just as quickly as they appeared. Other passages broke away in random directions, some being directly exposed to the nightmarish world while others seemed to lead down tunnels like the one they ventured through earlier. The air was heavy with the stench of sulfur and it made it difficult to breathe.

Bizarrely shaped skeletons belonging to creatures that Twilight was unfamiliar with laid next to some artificial walls they passed. There appeared to be large, curled horns protruding from some of the skulls, but others had numerous small spikes covering them. What must have been tails laid curled up on the ground between the legs of some of the dead. The spines on the vertebrae of some of the creatures looked bigger than they should, and the unicorn bit her lip as she pictured what they must have looked like when they were still alive. She quickly side stepped past another set of bones that laid sprawled out with a clawed hand extended, almost as if it was lunging to attack her.

Twilight heard screeches of terrifying, winged monsters flying overhead through the impossibly high, bronze sky. She had no idea how big they could be in the distance, but she had no desire to find out. The fact that they were there in a perfect position to snatch her away without warning was enough to make her want to duck behind a rock and never come out. That is, until she heard the chattering of an indecipherable language being spoken by who knows what coming from the shadows. She swung her head in its direction and saw small silhouettes, complimented by tiny yellow eyes, ducking into the darkness upon being spotted.

Twilight wanted to scream. She wanted to run back to the gate and smash it open, leave this forsaken place, and simply figure out a way to never sleep again. But she couldn't. She needed to have faith in Celestia. She hadn't flinched once at the horrors around them or said anything since before they entered. The Princess could handle any threat that tried anything, even in this place, right? She was able to make Cerberus, the fierce guardian of the gate to Tartarus, back down with some strong words. Even so, they were in Tartarus.

After about another hour of pushing deeper into the bowels of the goddess-forsaken world, a large throne comprised almost singularly of fanged skulls appeared at the top of a small, smooth set of stairs in the distance. It sat overlooking a massive, circular clearing with several footpaths emptying out if it, presumably leading to other equally horrific areas.

Twilight swallowed her fear, but her shaking gave her away. Her heart started racing. There was only one thing that would require a throne in a place like this. A few pebbles suddenly clacked against a large stone behind them and Twilight spun around. The silhouettes were back and all around them now, leering at them curiously, but this time they didn't run off. Instead, they snarled and giggled at their guests. Celestia continued toward the empty throne, unphased by the devilish imps in their presence.

With only twenty feet separating the two mares from the sickening chair, their little visitors suddenly darted away in a panicked state, shrieking and chirping loudly. The sky lost its hue and became noticeably darker. Unsure of what to think, Twilight gasped and curled up against Celestia's leg. The Princess kept her eyes forward as she had the entire time. Out of seemingly nowhere, trails of living fire appeared from the left, right, and above and spun into a ball in front of the throne. A form began taking shape.

One by one, four long legs extended to the floor. A slender neck next. Then, an equine body and head with a horn as long as Celestia's. Finally, a set of wings, devoid of any flesh, extended from the creature's sides, flapped twice and retracted, the bones and sinew crackling as they moved. The flames shrank away to reveal a bluish silver coat. The mane and tail, however, continued to burn. A white pony skull appeared on his flank. The demonic alicorn now standing before them opened his dark green eyes and smiled drily.

"Oh, Celestia, it's so nice to see you again after all these centuries! I was beginning to think you had forgotten about me!"

Author's Notes:

Apparently there was a problem getting this thing to show up on the list, so I had to resubmit this chapter. Grrr.

Anyway, for those suddenly screaming 'Ah mah gahd, an alicorn OC!', relax! His story will be revealed soon! I think you may even like it! At least I hope you do. Enjoy!