"Rarity!" I boomed, my demon voice reverberating around the new cavern. "Senorita! We have come to save you, Senorita Rarity! Where are you, mi hermana?" I heard Twilight whisper behind me.
"Fluttershy, I think you broke him..." she chuckled. Fluttershy giggled quietly, hooves cruching stones beneath her. After the stare, she scared me. Now, after that 'morale boost', I'm fucking terrified of the timid Pegasus. I nervously cast a glance behind. I'd taken the rear of the group, followed by Twilight, Fluttershy, Sky, and Solar. Twilight's horn was aglow with a lavender aura, illuminating gems hidden in the walls. Since we were all kind of on edge due to the roars of an unknown beast, Solar and Ebony had taken to using a life-detect spell during each roar. Everypony was glowing blue or red, different colours depending on whichever of the two unicorns was performing the spell on them. However, in the distance, we were all fairly certain there was a blue glow that seemed to be slowly getting larger the further we went from it. I looked back to the front.
"At this rate," I muttered to myself, "I'll miss my frickin' date. Or meeting. Whatever."
Meeting.
Hey.
Hello. Well, since we haven't already, we have...come to apologize.
Why?
For our behaviour a few days ago. We were slightly wine touched, and-
No, no, it's alright. Slightly violating though.
Yes, we know. Sorry, a million times.
Oh, I need to ask: when's that carriage due to arrive?
Ummm...7:00 sharp, we believe.
Ok, thanks. Needed to know.
Why would thou need to know so much?
Erm, I'm kinda...sorta...rescuing Rarity from Diamond Dogs.
Oh? Feeling heroic, this day?
No: I got dragged along.
Well, still a story. Try to bring along anything thou may find; after all, those caves thou art in haven't really been fully explored by ponies.
Oh, and I just need to warn you about something.
What could thou need to warn us of?
Errr...there's some kind of monster down here that's been following us and reminds me of a fictional beast back in my dimension?
Thou must be jesting. Which beast?
Terramorphus the Invincible.
WHAT?!
You sound worried.
Yes, we are EXTREMELY worried for your safety! That beast used to terrorize Ponyville, Canterlot, Manehattan, everywhere! Avoid it at all costs!
O-Ok...what if we can't?
Fight it. 12 ponies, if you manage to find Miss Rarity, should be a difficult fight, but there is three times the chance you can defeat it.
Wait, that sounds famili-
It was banished to those caverns by 4 brave ponies. However, they never returned from their adventure. Personally, we believe the creature ate them.
Y-Yeah...I-I feel motivated by th-that statement...
And, if thou were to defeat it, we would reward thy companions handsomely...
Are you implying...?
Thou would be correct in assuming riches, glory, and mares.
Dayum. I'll try to beat it if it attacks. Unless, you're joking...
We do not jest. We never jest.
Well, the other night you 'jokingly' began to seduce me...
Silence.
Alright, Lulu.
SILENCE. NOW.
Jeezus, fine...
Errm, apologies. We shall see thou tonight, 8:30.
Alright.
And Thunder?
Yes?
10 days notice next time. Promise.
Ha, alright Miss Smarty Lingerie. See ya tonight.
"Guys." I said aloud. "Luna went into my head again, so I asked her about the creature." Rainbow hovered next to me, looking into my eyes expectantly.
"And?" she asked excitedly. "What'd she say?"
"She confirmed it was Terry, and to avoid it at all costs. Apparently it was banished here a thousand years ago by four brave ponies, who were promptly eaten." The group stopped in shock. All pupils in the area promptly shrank. Suddenly, a female cry split the air. Twilight's ears pricked up excitedly, a smile going to her face.
"That was Rarity!" she quickly said. Spike wasted no time in jumping onto Twilight's back, raising a sword shaped stick, and shouting.
"Hi ho Twilight, AWAY!" the dragon shouted bravely. Twilight simply turned, glared at him, and levitated him onto the floor again. The dragon looked upset, so I grinned from behind the skull.
"Hop on, warrior!" I laughed. The little lizard grinned, and leapt onto my back.
"Hi Ho Thunder, AWAY!" Spike shouted once more, pointing his mighty ebony blade forwards. No, seriously, it was ebony wood. Strong, but not as strong as box wood.
"Hold on, we're comin' Rarity!" I yelled, rearing up and galloping forward. I honestly felt awesome; I had a skull for a hat, there was a dragon riding on my back with a 'sword', and I was charging forward followed by the others. After a few sharp turns, we found the central cavern. It was even bigger than I expected. Huge gems encrusted the higher walls that the dogs presumably couldn't reach, smaller gems speckled the dark stone walls like oregano on chicken. Or some other shitty metaphor. All 11 ponies, plus the mighty Dragonborn on my back, took the dogs by surprise. None were wearing armour, carrying spears, or prepared. Instead, the few with mining tools dropped them as we began our assault. The battle was rather one sided; we ponies rounding the dogs up, the ones who fought back receiving a vicious smack from Spike's blade. The odd one or two managed to flee the cave, but didn't come back. In but a few moments, we had gathered every single dog, tied them up, and left them in a cart. Once we were sure they weren't going to escape, I trotted over to a cart in the far corner of the tunnel. Tied to that cart was a certain white and purple mare, smiling now that she had seen us TOTALLY kicking those dog's asses.
"Took your time." Rarity laughed as Spike dismounted my back, waddled over, and disconnected her from the wagon. I looked at the contents of the cart. There had to be well over 1,000,000 bits worth of gems in there! Red, green, purple, blue, yellow, every single size, shape and colour could be seen, and that was just the top layer of the pile. After a few moments of marvelling at the quantity of the gems, I turned to Rarity.
"Good to see you." I boomed, extending a hoof for her to shake. She took one look at my mask and rolled her eyes.
"It's an improvement, Thunder." Rarity smiled. "Better than your fe-"
"DON'T BRING IT UP." I roared. "And besides, that voice was sexy. Like, British female pirate captain. They're always sexy."
"Rarity, what does 'sexy' mean?" Spike asked. Rarity turned, smiled at him, before levitating a clump of gems to him. The dragon giggled excitedly, before charging off with his dinner.
"Clever."
"I am aware." Rarity laughed. "Are we going to leave now?"
"Yes. But, we'll need to avoid an ancient monster Thresher called Terramorphus the Invincible, and we need to get back to Ponyville by 7:00."
"Why? And please remove that head: it's side effect is rather off-putting." I did as she asked, and replied.
"Well," I began. "Princess Luna has requested to meet me in the flesh, and a carriage is arriving at 7:00 to take me to Canterlot for a 'date'. She claims it's a meeting, but most likely not." Rarity had her jaw agape with surprise.
"Princess Luna?" she asked. "Wow, Thunder, I didn't realise you were capable of such achievements."

"Neither was I. Now, shall we see about getting out of here?"

It was behind us. So we ran. A new route we found led us straight to the surface, and onto the same place we were in originally: same pile of dug up crap, same path I took with Dashie, same everything. Except this time we were being pursued by a bloody gigantic Thresher my friends and I thought fictional. Then again, we also thought ponies were fictional, look where that ended up. I instinctively cantered over to the pile with my friends. Quickly turning to the girls, Inferno yelled over.
"Girls! Go! Run now!" he shouted. "We'll be fine! I'll come back Twilight, I promise!" Twilight looked on the brink of tears, before quickly swallowing her fear, nodding, and running off down the mountain with the other girls. The moment they were surely out of sight, my male friends began to arm up with old armour and weapons we'd dug up. I selected a simple sword-and-old-piece-of-sheet-iron combo, whilst Ebony, being the only one of us who could lift it, elected to choose a hulking battleaxe. He levitated in by his side with a blue aura, equipped a bashed-to-shit chestplate, and nodded. I held the sword in one hoof, before positioning my -ahem- shield onto my other leg. Promptly, Solar picked up a spear, helmet, and boots. Inferno went for a visor-fitted helmet, before picking up a machete. I was surprised this stuff even existed in a peaceful place like Equestria. Fire Trail put on a hulking pair of spiked boots, thick chestplate, and nothing else. He looked at us.
"I'm the motherfucking Juggernaut." He growled. We laughed, before continuing our search. Sky, finally, had settled with two axes he wrapped in his wings. Nodding, saying our last words (we presumed), we turned...
And then ran down the mountain like a bunch of fucking pussies, yelling and looking back as the huge tentacles shot up from the place we were stood a few moments ago. Seeing no other options, I told Sky, Inferno, Ebony, and Solar to try getting us back quickly.

"TELEPORT US! FLY! WHATEVER! JUST GET US BACK ALIVE!" I yelled over the extremely loud Thresher noises behind us. The earth shook and boomed, rocks fell, and the ground parted beneath our feet. Just before Terry grabbed us, there was a blinding flash of purple light as Ebony and Solar magicked us all away at once.

From back in Ponyville, I doubt Twilight could comprehend what had happened. She claims we disappeared by magic, appeared in Ponyville, before Terramorphus stopped. Apparently, the poor fellow simply waved his tentacles, looked around, made a loud, sad sounding noise, before slowly making his way back to the caverns.
Whatever happened, it would be an awesome story to tell Luna.

Author's Note

Got bored. Thought it needed Terramorphus, and then I presumably just murdered what little enjoyable-ness this story had. Feel free to piss on my grave when I die. Y'all have fun now.