"I-I like to think I speak for all of us when I say ZOINKS!" Mikey whimpered, as the four of them backed back into the lab. The blue one spat acid directly in front of them, causing them to yelp as it burnt a hole straight through the floor.

"Right…" Mikey joined his brothers in pulling out his weapons, "… you guys can take the three on the left."

"… There are only three!"

"Yep. One for each of you and I'm just going to be the odd one out."

Raphael rolled his eyes, "You and Donnie stick together. If you leave him alone, I promise I will end you, understood!"

"I- "

At that moment, the red creature threw a console at that, splitting them into two groups. Mikey stood there in stunned silence as the red creature grabbed Donnie in one of its' pincers, not even flinching as Donnie attempted to shock it again and again.

"Mikey! Mikey!" He called, "Electric eel! Electric- AAH!"

He was thrown to the ground, landing heavily with a THUD. Winded, he couldn't move as the red creature moved closer.

"Hold on Donnie!" Raph suddenly came charging out of nowhere, kicking the creature into a nearby wall, before checking on Donnie, "Are you okay?"

"Y-Yeah, just a little…" Donnie sucked in a desperate breath, "… winded."

Raphael nodded in relief, before spotting something on the ceiling. The rock-like creature was climbing along the top of the room, before eating and burrowing into it, moving through the ceiling until he stopped directly above a shell-shocked Mikey.

"MIKEY, MOVE! CHANGE! SHIFT! DO SOMETHING!"

Mikey didn't move, prompting Raph to push Donnie behind a piece of fallen console and dive forwards, knocking the rock monster off course.

"Watch your back, you oddball!"

"Odd?" Mikey frowned, not seeming to notice how the rock monster tackled Raph to the ground, "I'm not odd… I'm eccentric."

"AAAAH!" Donnie skidding across the floor, hitting Mikey in the legs as he gasped for air. Wincing, Mikey helped his younger brother to his feet, putting Donnie behind him.

"Raph just called me odd!" Mikey whined.

"You're just being sensitive!"

"I am not!"

Across the room, Leo was riding a gurney, using it to knock the blue creature into a nearby console, electricity coursing through it as it fell to the ground.

"Can we swap creatures?" Donnie called out to his oldest brother, hitting the red creature furiously, "My powers are useless against this one!"

There was no answer, as they continued to fight.

"I know these monsters are vicious abominations…" Mikey lazily batted away rubble with his nunchuck, "… but we are not holding our own out there! You can do it!"

"Shut up Mikey!"

…

Leo yelped as the glass in the containment units cracked, a green liquid spurting out.

"You will take no more of us!" The blue creature hissed at him

"What? We're not here to take anybody!"

The containment unit started to wobble, as the blue creature seemed frozen in shock staring up at the unit. Seconds before it was crushed, Leo dived forwards, tackling the creature to safety.

"Why did you attack us?!" Leo asked, "We didn't- ARGh!"

The red creature punched him into the wall, Mikey catching him mid-air as a gorilla.

"You know what Mikey…" Leo groaned, "… I think they think we're someone else."

"Well that's just brilliant. We're getting our asses handed to us, and it's someone else's fight?"

Spotting Leo and Mikey, the other two rushed over, just in time to catch the end of the conversation.

"I vote we get the hell out of here!" Donnie yelled.

"Run away?" Raph frowned "That's not my style!"

Leo rolled his eyes, "Let's call it a tactical retreat then. Come on!"

Donnie short-circuited the doors, forcing them to open as three of them raced through, leaving Raph alone with the three creatures.

"Tactical retreat…" He winced, "… I can live with that."

They all ran into another room, that had a large metal door on the other side.

"It's sealed shut!" Donnie yelled, pulling on the wheel to try and open it, "Mikey, can you shift into something a little stronger!"

"Not if we want to get out in the next few seconds… unless- "Mikey shifted into an elephant, pressing up against the open door until it was firmly closed, the creatures roaring on the other side.

They were officially trapped.

Large dents started to appear in the door as the creatures fought to get inside.

"Does someone want to get that?" Mikey whimpered.

It only took a couple more hits before the door crumpled in on itself, as the red creature filled the doorway. By the other door, the rock creature popped out of the ground, cutting them off in that direction.

However, before the creatures could attack, the blue one darted in front of the red. "STOP!"

For a moment, everything was tense.

"Just say the word Leo." Raph hissed.

"Wait…. It's all okay."

The blue creature leaned in and sniffed at Leo, before frowning. "Who are you?"

"Not who you think we are!"

"Then why do you carry those?" The blue one pointed at the duffel bag Donnie was carrying.

Donnie frowned, pulling open the zip to reveal the blue crystals, causing the creatures to let out a threatening rumble.

"Woah, woah!" Leo stepped in front of his younger brother, "We found these crystals in a cavern where we're living. That's it!"

"Yeah!" Raph nodded, "And what business is it of yours anyway?!"

"Those crystals are the embodiment of evil!" The blue creature snarled, "Why have you come here?!"

"Because one of you ogres came sniffing around our place, looking for trouble, so we're here to- "

Donnie quickly covered his brother's mouth, "- look for some answers! We're just here to look for some answers."

"I'm Leonardo." Leo introduced, "And these are my brothers. Raphael, Michelangelo and Donatello."

"We were drawn towards your habitat when the crystals were activated." The blue creature explained, not noticing how Donni sent Mikey a vicious glare, "Their energy is a sign of danger to us, so we considered you to be dangerous. Though we usually sense them deeper below."

"Below?" Donnie tilted his head to one side, "You mean that there are more of these crystals down there?" He followed the blue creature as they turned away, "We just want to know where they came from, that's all, and maybe- "

He was cut off as the blue creature suddenly spun around, slashing at Donnie as his older brothers pulled him to safety, Mikey making sure he was between it and Donnie.

"No!" The creature snarled, "That place is forbidden! Something unspeakable dwells there amongst the crystals… there are some things man was never meant to tamper with."

Donnie slapped his hand over Mikey's face, stopping him from speaking as the creatures looked over in confusion.

"He is an odd one." The blue creature scanned Mikey from head to toe, before leading them back to the lab.

On the way, Mikey clung onto Raph. "I don't trust these guys!" he hissed.

"Why?"

"Try the fact that they're monsters!"

Donnie, who overheard the whispered conversation, frowned. "Yeah well, to some people, so are we."

Mikey shut up after that.

"I can't believe the Shredder had you genetically modified as diggers, just to try and find some… enemy." Leo shook his head in disbelief.

"Yes. And he did so without remorse! We were forced against our will to do his bidding!"

"He just snatched you at random? From where?"

"The streets. Our offices. Our homes. Anywhere a shadow can conceal a Foot Soldier." The blue creature shrugged, "We don't know why we were chosen."

Realising that he couldn't keep referring to them by their colours in his mind, Leo cleared his throat nervously, "So, what's your name?"

"I am Quarry, of Tunnel Squad Three." Quarry gestured to the other two, "These are Stonebreaker and Razorfist."

"No." Leo shook his head, "Not what the Foot called you. What are your real names?"

"Si- Si- "Quarry shook their head, "My memories- the experiments performed on us have stripped us of who we are!"

"Yeah… we saw the video-log entires."

"Well, don't worry about Shredder." Raph interjected, "He got his comeuppance."

"Yeah!" Mikey beamed, "He made the mistake of messing with us! And there's a lesson to be learnt, if you know what I mean."

Before Quarry could say anything, an alarm started to blare up ahead, a red light blinking on the screen.

"Oh no!" Quarry raced over to the screen, "The others! They've tripped an alarm in the East Delta tunnel! We need to activate the energy shield!" They tapped at the computer frantically for a few moments, watching as the crystal whined and flickered, before going dim, "No, no, no!"

"Don't do a no, no, no!" Mikey whimpered, "I hate no no's!"

Quarry snarled, turning their attention to the other two. "It's no good! The shield won't activate! We have no power! No forcefield! And they're heading this way."

"Um." Raph sheepishly rubbed the back of his head, "Yeah, we kinda met your forcefield."

"And Raph kind of… broke it!" Mikey smirked, yelping as Raph hit him around the back of his head.

He yelped again as a roar echoed through the lab.

"What's out there?" Leo asked, eyes trained on the open doors and the darkness beyond.

"The others."

"What others?"

"Other test subjects, like us. They endlessly prowl the tunnels."

"…. Why do you have to keep them out?"

"Because they're violent!" Quarry ripped the metal off the computer system, "They're aggressive and they attack us! They're uncontrollable! Their minds have completely deteriorated!"

"From the genetic mutation?"

"…. Yes."

"So, what about you three?"

"Madness looms in our future too."

Another roar echoed through the tunnels, as Quarry tapped two wires together, watching as the crystal once again flickered and died.

"It's no use!" They hissed, "The crystal's completely burnt out… It's hopeless."

Another roar.

As the brothers all tensed up, pulling their weapons out of their sheaths, Quarry shook their head. "Weapons will be of no use here. Without the forcefield, we won't stand a chance. They'll be on us in minutes."

"You know, you're really freaking me out here!" Mikey frowned, "Are you always such a- Donnie, what are you doing?"

Everyone turned to see Donnie climbing up to the crystal in the machine, wrenching it free and watching as it crumbled to pieces. "Is that what the crystals are?" He asked, "Power sources?"

"Yes, but that was our only one! And when we found it in the catacombs, we paid dearly for it."

"What about one of ours?" Leo rummaged through the duffle bag, pulling out one of the crystals and moving to hand it to Donnie.

"It's too small!" Quarry shook his head, "It wouldn't last."

Donnie didn't seem to care about that, plucking the crystal from Leo's hand. "It only has to last until they give up and move on! And I can give it a boost if needed."

The crystal did nothing, even as the roaring got closer, prompting Razorfist, Mikey (in gorilla form) and Stonebiter to rush and close them.

"There's no spark!" Quarry yelled, watching as Donnie tapped the crystals together, sending off random jolts of electricity into the machine in a hope to start it.

"For some reason, it just won't start up!" Donnie examined the machine a little closer, "Maybe the connections to these contact nodes were charred?"

"Or maybe you've put it in upside down?" Mikey piped up.

"It's not upside-down Mikey!"

The creatures thumped on the metal door, as Stoneface and Razorfist fought to keep it closed.

Tinkering with the machine, Donnie pulled away, "Alright, let's try it again!"

The door smashed in, and the creatures slowly entered the room. Donnie hesitated putting the crystal in for a moment, before slowly turning it over and placing it in the machine, sighing in relief as it flickered to life.

"It's working!"

The forcefield pushed the creatures back out of the room.

"Don't think I didn't see that Donnie!" Mikey smirked, "It was upside-down!"

The crystal seemed to be struggling though, flickering occasionally as Quarry started to panic. "It's overloading!"

For a few seconds, it seemed like the creatures were going to break through the shield, until finally, they started to move away.

"They're leaving." Quarry confirmed, "But they'll be back. They always come back."

"Then you'd better have a bigger crystal." Leo glanced over at the current crystal, which seemed to have completely burnt out.

"We will not survive any journey to the forbidden zone."

"What makes the place so… forbidden?" Mikey asked nervously.

"The ancient catacombs stretch for miles. We were forced to explore it, and many of us never returned."

"Maybe they got lost?"

"They were taken by a ghostly entity! There is never any sign of a struggle. They're just… gone."

"Look." Leo pushed down any uneasy he might have had, "We get why you don't want to go down there, but right now, you don't have a lot of options. You need another crystal, and fast!"

"And since were the ones who… kinda fried your security system, we'll go with ya!" Raph beamed, "Right guys?"

The others all nodded in agreement… well, except for Mikey.

"You know, the hardware shop on the corner is doing a deal on generators. One of those will really get this forcefield running. So, I'll go up top, clip the coupon and- "

"- Come on Bozo!"

….

They made their way into the catacombs, the creatures all whispering reassurance to each other, as the four brothers stayed close.

"Okay, let's keep our wits about it." Leo quietly spoke up, as Raph turned back to his twin.

"Don't worry Mikey, you can have some of my wits."

"Oh, so now I'm witless?" Mikey rolled his eyes, "Must be why I'm the only one bothered by the fact that we're heading into a place that even monsters find scary!"

They headed down a spiralling path, into the darkness.

"There's a shortcut to your left."

And there was…. a slide. Screaming, they all landed in a pile at the bottom.

"A shortcut?!" Mikey groaned, "In what mutated imagination can that be considered a shortcut?"

"Sorry." Quarry apologised, clinging to the walls along with their friends, "We forgot that you can't scale rock."

"Actually, I can! If given a little bit of warning!"

"Let's just try and avoid that mistake in the future, okay?" Raph slowly got to his feet, helping Donnie up, before stretching out his own aches and pains.

Mikey then pulled a face, "Ugh, who cut the cheese?!"

"You're smelling a sulphur pool Mikey." Donnie gently explained.

"Speaking as someone who grew up in a sewer, trust me when I say, this place stinks!"

"We must keep moving." Quarry ordered, "The others often wander down here. This is their territory." They headed over to the pool, hopping across it using the rocks.

Any unfortunate creatures that happened to pop up were promptly eaten.

"Ew." Leo muttered, wincing at the sound of crunching from Quarry's mouth.

"We learn to eat and live off the land… for it lives off us."

…

The next stage of their journey involved walking along a narrow path, pressed up against a rocky cliff face, whilst Mikey flew anxiously nearby.

"Donnie, stay close to- WOAH!"

"Leo, are you alright?!"

"That… was a little too close for comfort." Leo kept his eyes on the ceiling, "Just watch your footing."

They then headed out onto a narrow bridge, which was over a swirling whirlpool.

"This is it." Quarry stated, as Razorfist jumped into the whirlpool, closely followed by the other two.

"Okay…" Leo looked over the edge, "… following monsters off a cliff into a whirlpool may not be the smartest thing we've ever done."

"No, but it is the grossest." Mikey reported from above, "That thing looks like a giant toilet! COWABUNGA!"

…

Falling down a waterfall, Mikey shifted into a fish in a desperate attempt to get to solid ground, only to struggle against the current.

And then the mouth picked him up, making Mikey panic as he was shrouded in darkness.

"Spit him out Stonebiter."

With a sickening noise, Mikey landed on the ground, transforming back instantly and gasping for air. "You have hands!" He gasped, "HANDS!"

Ignoring his younger brother, Leo turned to Quarry, "How far away are we from the crystals?"

"They're here in the catacombs… but from this point on, we must be absolutely silent."

They headed up a rocky hill, as Donnie turned to Mikey. "Hey, recognise these carvings?" He held the crystal up slightly, so that Mikey could see.

"Woah… they're just like the carvings at home!"

"Yeah." Raph muttered, "Same interior decorator."

They all headed into a tunnel, nobody noticing how Mikey stopped and glanced up at the ceiling… which seemed to be crumbling.

A little way inside, Quarry spotted a crystal in the wall. "Good. This one will do. We need not travel any further into this accursed place."

Outside the tunnel, Mikey yelped in fear as one of the 'others' chewed through the ceiling, transforming into a cheetah and racing into the tunnel, as the creature landed behind him.

Mikey sped past the others, screaming about the monsters behind him.

"We need to get to cover!" Leo yelled, rushing further into the catacombs.

"But that leads to- "

"- we have bigger problems right now!"

Coming up against a giant stone door, which even the creatures couldn't get through, Donnie spotted a small hole which seemed to fit the shape of the crystal in his hand. Thinking quickly, he shoved it into the gap, only to groan when the door refused to open.

Even the creature's acid wasn't enough.

"I wonder…" he muttered to himself, as the others all got into their battle positions. Slowly, he reached out, and turned the crystal around, beaming as the crystal glowed and the door opened up. "Hey!" he ran inside, "It worked!"

The others all turned, just in time to see a glowing ring surround Donnie before… he was gone.

"DONNIE!" Mikey screamed, as the other two echoed his panic.

"DONNIE!"

"DAD IS GOING TO KILL US!"

The creatures were coming a closer, as Quarry sighed wearily, wincing at the dismayed cries of protest coming from the three remaining brothers.

"This is where it ends."