Hoofsteps echoed through the damp air of the tunnels below the Dustwatch, Moonlight had not entered with Twilight and Dash as she had gone back to get the earthponies. Twilight had been marking the way they had been walking with chalk so the others would easily be able to find them once they also entered the catacombs.

Dash meanwhile was obsessively scanning every nook and cranny she found for evidence of her little sister, they had already found a couple of orange feathers along the path they were now moving through.

"Dash, you need to slow down to allow the others to catch up," Twilight told the pegasus who had yet to show any signs of slowing down.

"Can't. Have to find her." Rainbow simply answered as she continued barreling down the underground hallway deeper into the mountain upon which the Dustwatch was built.

"Rainbow, if we find her we're also going to find the things that took her. We. Need. Backup!"

"I DON'T CARE! I'M NOT LOSING HER AS WELL!" Dash shouted at the unicorn trailing her as she jumped around to face her companion, her voice echoing through the tunnel.

Twilight meanwhile looked at Dash with a sudden curiosity, "What do you mean with 'as well'?"

Dash suddenly stopped moving entirely, "I-I promised her parents I would make sure she'd survive, unlike her bigger sister." She softly said as tears started rolling down her face. "That older sister was my best friend at the time, she was extremely shy and a terrible flyer but the kindest pony I've ever met."

Dash paused for a moment as she struggled to find the right words, "Did you know that at the age of twelve pegasi are thrown off the cloud city they were born in to see if they have gained enough flying skills to get back up?"

Twilight shook her head as the specifics of pegasi culture weren't taught in the empire, seeing as the pegasi were portrayed as little more than dishonourable raiders.

"When my class was thrown up it didn't take very long for me to get back up to the clouds just like the rest of the class followed soon after... she never got back up to the cloud and once someone went down to see if they could find her body they never did. After Scoots was born I promised her parents to keep that filly safe whatever the cost so before the same thing could happen to squirt I ran away, the rest you know." Dash told Twilight as she turned to continue further down the tunnel, "That's why I can't slow down Twi, I already failed her once in not going after her. I'm not letting her little sister go as well."

With that Dash went on and ran at her previous speed down the tunnel. Twilight, though still of the opinion that they should have wait for the others, ran along with the pegasus who was clearly not going to be dissuaded as two ponies were still better than one in a fight.

The furter into the mountain they ran the more the wallways started to look like actual caves instead of constructed passageways, also along the walls clusters of a hardened green goop of some sort started appearing the deeper they came. Sounds of walking creatures had also slowed down Dash's and Twilight advance as they were now sneaking down the tunnel to avoid being spotted for as long as possible. A couple of minutes of sneaking later they could see a dim green light in the tunnel ahead. Turning a final corner we were faced with what could only be described as a horror scene. Green pods lined the walls of the tunnel they had entered, each and every single one containing an earthpony who were seemingly unaware of their surroundings.

"This is horrible" Twilight whispered while Dash's anger only seemed to increase at the sight of the hallway.

"And my sister's somewhere in here" Dash growled as she slowly moved forwards on three legs, keeping her extendable blade poised to strike at any moment. Twilight similarly took her short sword in a telekinetic hold beside her as she closely followed the pegasus.

Suddenly Dash saw movement in the corner of her eyes and quickly turned, slashing at the thing beside her, a raspy screech could be heard as a black pony of some sort dropped onto the ground. Chitin covered its body, though its legs seemed to be full of holes, and a pair of insect wings sprouted from its back just as a jagged horn sat on its head.

"Where. is. my. sister?" Rainbow slowly and darkly asked as she held the bleeding bug-pony up against one of the pods with her sword pressed against its throat.

The blue insectoid eyes seemed to be looking up at the pegasus in fear as it responded with a raspy voice, "I don't know, the Queen wanted to see the sky pony herself!" It whimpered.

"And where might she be?" Twilight asked as she kept an eye on the surrounding hall, just in case they had missed another one of these bug ponies.

The bug pony looked terrified as it stuttered its answer, "I-I will not betray my Queen!" This angered Rainbow, a low growl came from the pegasus as she pushed the sword slightly deeper into the bug pony's neck.

"Where is she." Dash once again asked, the bug screeching in pain but stubbornly refused to answer.

"I will not ask again, where is my sister." Rainbow threatened for the last time as she pushed her blade even further into the neck of the creature.

"I will not..."

Before the bug could finish Dash pulled back her blade only to jam it deep into the creature's skull, killing it before it even hit the ground.

"It was wasting our time, we should continue on, maybe the next one will cooperate better." The pegasus stated to Twilight who was baffled by how violently Dash had killed the bug. Rainbow didn't give the unicorn time to respond as she continued sneaking through the caverns where they found a few more hallways where ponies were trapped in the green cocoons.

Only a few minutes later the two infiltrators could hear voices echoing through the tunnel. Crawling around the presumed last corner they finally entered a very large cavern which had multiple other caves leading into it, in the centre of this large cavern more of the bug creatures roamed and flew around, performing various tasks. Though that wasn't what caught Rainbow's nor Twilight's eye, that was the large black bug on a throne of some sort and a small orange filly who lay unconscious in front of some of the bugs.

"Anything else to report, Delilah?" The larger but skinny bug asked, her stature and position on the throne clearly giving away that this one was the Queen of these creatures.

"We have captured fifty residents, which should provide us with enough love to start replacing some of them instead of just kidnapping them." It stated, the Queen seemingly approving.

"Continue our operation for another week to store a buffer of love. Also, take this Sky pony away to a pod, it is a curiosity but ultimately of no use to me." The Queen answered, Dash nearly seeing red as one of the bugs dragged Scootaloo along the floor with it.

Twilight tried to stop the pegasus before she could jump off the raised entrance to the cavern they were hiding in, but Dash's speed meant that she was already in the midst of the group dragging Scootaloo before Twilight could even begin casting a spell.

The first creature, that was dragging Scootaloo, received a sword to the neck as Rainbow came down, severing its spine and collapsing it immediately. Three more of the creatures that had been standing close to the first were swiftly taken out by Dash before any response came from the creatures that had been taken completely off guard.

Twilight saw one of the smaller bugs light its horn with a sickly green aura as it readied a spell. Grumbling a curse to herself she jumped down after the pegasus, making a roll to reduce the impact with the ground while simultaneously using her sword to take out the bug that had been charging its horn.

Coming out of their stupor at the swift execution of five of their number the Queen started shouting enraged orders at the smaller ones, "GET THEM!"

Dash and Twilight both took a position next to the unconscious form of Scootaloo while making sure none of the bugs would suddenly charge, only what happened next neither the unicorn nor pegasus could have predicted.

Every single one of the bugs suddenly caught on fire and turned into exact copies of the two ponies.

"Dash?" Twilight softly said as she looked straight into the eyes of one of her copies.

"Y-yeah?" Dash stuttered as her rage had faded a bit and she realized how screwed they were without proper backup.

"Only go after copies of yourself to prevent hitting me," Twilight instructed, the copies of the two ponies circling the trapped ponies while seeking an opening to attack.

Seeing a green glow coming from one of the Twilight copies the real Twilight quickly turned and put up a shield, her sword clattering to the ground as she switched spells. Thinking this was the opportunity to strike, the one bug released its spell while a couple of the other copycats charged only to run straight into the slightly visible shield. Not wasting a second Twilight dropped the shield and picked up her sword to take a swing at the dazed bugs, taking three more of them out before the last one managed to retreat back to a safe distance.

"WHAT ARE YOU WAITING FOR?!" The Queen shouted at the remaining bugs, while stumbling back towards a cave herself. The creatures even after being shouted at were hesitantly looking at Twilight and Rainbow. Given that the bugs weren't charging them, seemingly out of fear, Twilight took the time to study the creatures that hadn't changed. If the bugs were anything like ponies they looked like they were starving and possibly weren't even combatants as their combat performance up until now was suggesting.

Suddenly one of the circling copies of Rainbow burst into flames and turned back into a bug just before dropping onto the floor, followed by two copies of Twilight as the real Twilight saw knives stuck in the necks of the fallen bugs. Only a moment after two fully armoured earthponies smashed down from the same ledge the unicorn and pegasus had come from.

"Y'all seem like ya can use some help." Applejack said as she fixed her Stetson hat back on her head and pointed a spear in the direction of the bugs, Big Mac doing the same. The bugs seeing the two heavily armoured soldiers retreated back towards their Queen and took a defensive posture around her. More bugs fell around the Queen with knives sticking out of their bodies in various places as the two earthponies, pegasus, and unicorn formed up and started pushing the bugs backwards.

"Give up, Changeling! There is no need for this bloodshed, you have failed!" Moonlight shouted down from the ledge while holding what seemed to be a throwing knife in her wing talon.

"That's easy for you to say, Thestral. Your kind isn't starving!" The queen shouted back at Moonlight who still had a throwing knife at the ready, "I will remember this for a long time to come." The queen snarled as her horn lit up, Twilight immediately put up a shield over her group while Moonlight threw her throwing knife but hit nothing as the space the Queen had just been occupying was empty and the live 'changelings' had disappeared with her.

The group could suddenly hear a rough cough as they turned around and saw one of the changelings that had initially attacked them try to crawl away while clutching a wound inflicted on it by Twilight. Dash growled but was beaten to the bug by Midnight as the bat pony looked down at the fearful changeling.

"Don't move, daughter of Vironect. I mean you no harm." Moonlight said as she started treating the wound on the changeling.

"What are you doing?" Dash asked as she looked confused at the bat pony while getting slightly angrier once again. Moonlight ignored the pegasus and continued to stem the bleeding of the creature.

"Moonlight I must agree with Dash here, you must have seen what they did to the earthponies when you got down here." Twilight agreed.

"Ah'm agreein' with them two, Midnight. Better to be rid of it before it can do any more damage." Applejack also

"NO!" Moonlight shouted back at the three others, "You know nothing about the suffering of the changelings, they feed on love and when the three main races fell into war their kind was almost completely wiped out! That they are still alive after almost a millennium is astounding, I will not kill them for trying to survive." She angrily stated and hefted the changeling, who had fallen unconscious, onto her back before flying up to the ledge where she disappeared back into the caves.

The leftover ponies stood still for a moment looking at the empty cave exit only to be brought to reality by a groan from behind them. Dash immediately turned around as she recognized Scootaloo's voice and picked up the waking filly into a tight hug.

"You two should get back up to the barracks as well, we'll get everything done down here," Twilight told Rainbow who nodded and also flew off towards the cave leading to the surface. With Dash gone, Twilight turned to Applejack who was doing her mighty best to avoid standing near or looking at the changeling corpses. Seeing this Twilight sighed and walked up to her companion,

"You know we had no choice but to take them out, right?" Applejack sighed, closed her eyes, and nodded in understanding.

"Ah just ain't used to seein' this many dead things at the same time. Ah mean the unicorns in Ponyville are brutal but nothin' like this." Applejack admitted as she glanced at the corpses. "Ah ain't no soldier like you or Dash."

"It's not easier for us either, AJ. Let's just get out of here." Twilight said as she took a couple of steps towards the exit only to stop as she realized something she probably should have done earlier...

The floor of the cavern was unnaturally flat.

Stopping in her tracks she turned around and increased the amount of light that was coming from her horn, the entire room now decently lit up. The supposed cavern wasn't natural but carved! Scanning the room further her eyes eventually wandered over the floor where they stopped.

"Applejack help me remove this thing" Twilight said as she started pushing the throne of the changeling Queen towards the side of the room.

"Can ya give a hoof as well, Mac?." Applejack said as she also started pushing even though she had no clue why.

"Eeyup," The stallion simply replied, the moment he put a bit of force against the stone chair it moved as if it weighed nothing.

"Thanks," Twilight said baffled at the display of raw power, turning back to the room afterwards.

"What did ya see Twi?" Applejack asked as the unicorn seemed to be stuck in thought while looking at the floor, a smile slowly growing on the unicorns face.

"Look at the floor, tell me what you see." Twilight cryptically said, drawing Applejack's attention to the ground.

"It's a sun?" The female earthpony said as she didn't immediately understand what Twilight meant, "and is that writing?"

"Yes! It's ancient ponish!" Twilight squealed, "It says, Speak truth and enter the vault of Honesty. We accidentally found the vault!"

"What's she talkin' about, sis?" Mac asked as he was thoroughly confused at the sudden freakout the unicorn had. Twilight completely ignoring the large stallion as she tried figuring out the riddle.

"We're huntin' a bunch of magical artefacts, one of them seems to be here." Applejack answered her brother while keeping her eyes fixed on the mumbling unicorn.

"They dangerous?" Mac looking concerned at her sister.

"Apparently the Empress will try to get our heads once she finds out but from what I hear it's worth it." Applejack answered just as Twilight seemed to have a solution.

"Truth!" She spoke in a language Applejack had never heard but the effect was immediate, the crack of stone rang through the chamber as the arms of the sun along with the centre sunk into the ground. The middle circle of the ring suddenly slip into two and revealed a staircase. The two earthponies just looked on in amazement as Twilight was clapping her hooves like a small excited filly.

"What are we waiting for? Let's go!" She squealed as she started making her way down into the 'vault'. Applejack and Big Mac following as Twilight's horn was the only source of light the two had since Moonlight had left with their lantern.

The Stairs weren't that long as they soon entered a chamber that had murals and more text the two earthponies couldn't read. At the end of the chamber, a large mural of two large ponies, one white and a smaller dark blue one that had both a horn and wings stood facing each other, in front of it a pedestal stood with an iron torque on top of it with a large orange gemstone embedded into it.

"To my sister, who expected ponies to tell the truth, no matter how hard it was." Twilight read from the text that was written above the pedestal before adding. "Which I failed to do."

The group remained silent for a moment, only for Applejack to step forward and touch the necklace. The gemstone momentarily lighting up in a brilliant orange light as the earthpony flinched, the light dying down again immediately after Applejack stopped touching it. The orange earthpony looking at Twilight as for advice but the unicorn motioned for her to try again, this time the crystal stayed inert.

"This is all mighty strange to me but Ah'm sure y'all will help me out with it."

"That we will," Twilight said as she turned to go back to the staircase they had gone down, looking back at Applejack with a smirk.

"Come on, Element of Honesty I think we should tell our friends of our progress."