Princess Luna burst through the doors of the room her sister was staying in at Twilight's Castle, having felt her sister having terrible nightmares.

Luna asked Celestia, "Sister, are you okay? I've sensed you having such terrible nightmares…"

Twilight came in with worry and asked, "What happened? I heard somepony scream…"

Celestia was taking deep breaths as she said, "Luna, remember that legend that involved our ancestor, and how he, a dragon, and some female warrior, defeated a monster long ago?"

Luna was a little puzzled as she asked, "You mean that story our parents told us at bedtime? What about it, dear sister?"

About a week had past, since that day, when a volcano destroyed the grand city of Canterlot. The pegasi had managed to clear the smog from the sky, though the ground, streams, lakes, and rivers remained polluted by volcanic ash. Many of the large dinosaurs that once flooded the city have moved on in their endless search for food, the sauropods, many small dinosaurs, the Stegosaurus pair with the Camptosaurus, Gaston the Gastonia, and the six raptors were about the only dinosaur species to remain. However, a number of other prehistoric creatures had arrived in the quaint little town, like a large number of bat-sized pterosaurs called Aurnoragnathus, devouring damselflies that in turn ate little parasites, and a large group of Mesozoic mammals called Megazorasodon.

Within the time frame of the pegasi clearing the volcanic smog, more herbivorous dinosaurs moved to the returning green pastures of Ponyville, among them were many Edmontosaurus that were herding with another herd of a species of ceratopsian, two distinct breeds of the same species to be precise. These dinosaurs were as large as a bison, with one breed housing a large, flat, bony lump on their noses, and another breed that housed a huge, rhinoceros-like horn on top of their noses. They are the North American ceratopsian, Pachyrhinosaurus, the thick-nosed lizard, among them was a young individual Pachyrhinosaurus that had a hole on his bony frill, accompanied by a female of the same age, and a tiny bird-like dinosaur called an Alexornis.

Pinkie Pie noticed the three and immediately zipped in front of them, saying, "Oooo! Hiya there! My name is Pinkie Pie, even though you all don't understand me, you three look so-so-so-sooo unique that I felt an urge to introduce myself. With that out of the way, Welcome to Ponyville strangers! What are your names? What are your favorite colors? What kind of meanie pants dinosaur did you beat up? What…"

The earth pony drove on with questions to the two Pachyrhinosaurus and the Alexornis, leaving them quite confused as the mammal in front of them seemed to be trying to communicate to them, but all they heard was what sounded like garbled-up static.

The Alexornis asked the male he was perched on, "Patchi? Is this pink mammal trying to talk to us?"

The female answered, "I think it is, Alex…"

The Pachyrhinosaurus named Patchi said, "I think you're right Juniper, Alex, what a bizarre creature these mammals are?"

Patchi, Juniper, and Alex then rejoined the herd as the ventured into the Everfree Forest, following the smell of food that seemed to be coming from inside the, surprisingly, untouched forest. They were also followed by a lone ankylosaur, called Sauropelta, this one was from the northern most part of North America, just past the Arctic Circle. Pinkie zipped into the ankylosaur's face, making the large creature step back in surprise, the smell of pollen from a basket of flowers the pony carried made the Sauropelta sneeze furiously, then walked to the direction of the Everfree Forest, with the Edmontosaurus and migratory Pachyrhinosaurus herd into the dense parts of the forest.

With scores of dinosaurs and various other prehistoric animals behaving as their species had for millions of years, it became very clear already that they are dominating this new world, and have already drove several creatures into extinction, a few include some wild cats and the Cragidiles. Many creatures that were flourishing on Equus, were now endangered, like the Timberwolves, Manticores, and even the mighty sea serpents were in danger of facing extinction. The only creatures that could hold on for a good long while, would be the dragons of Equus, but they were an endangered species themselves, getting killed by predatory dinosaurs that hunted them, or were killed by a herbivore that fended itself. But, some dragons were getting killed by something else, not only by diseases that killed reptiles, but were also getting killed by something else, another creature was actively killing these creatures, but it was a story for another time, how it ties starts when a visitor made its presence known in Ponyville…

About a day had past when the Edmontosaurus and Pachyrhinosaurus entered the Everfree Forest, Twilight Sparkle and her friends were watching the Stegosaurus and Camptosaurus with ambassadors from an underwater kingdom from the Equestrian Sea.

The princess of the undersea kingdom said with amazement, "Wondrous, we have nothing like these 'Stegosaurus' or 'Camptosaurus' in the ocean. But, we do have some fish and gigantic sea turtles that sound like they came from this, 'Mesozoic Era' that these dinosaurs came from…"

Rainbow Dash, being herself, said, "I doubt it, there's no way that a sea turtle can be as big as a carriage…I've seen them with Fluttershy, so I know…"

Twilight chuckled as she said, "Actually, Rainbow Dash…There is a prehistoric species of sea turtle that can grow to be as massive, if I remember correctly, it is called Archelon ischyros, a species of sea turtle that lived in the Cretaceous Period that can grow to be as big as sixteen feet wide and thirteen feet long."

Rarity added as she heard the measurements of the ancient turtle, "You know girls, over a week or two ago, I read a news article that fisher ponies found a lone pirate drifting on the shattered remains of a ship, and with the pirate and ship was the…ugh…corpse of a gigantic sea turtle that looked like it was bitten in half by something. I think it is relevant because the autopsy of the sea turtle's possible size when alive was a precise match to this 'Archelon' creature."

Applejack was a little pale after hearing that something bit a turtle the size of a carriage in half, as one of the Stegosaurus called out to its mate in the background.

"Princess Twilight!" a guard shouted.

Twilight responded as she said, "What's going on, why are you shouting?" The guard looked pale as he said, "It is urgent! Come to the water reservoir, there's…"

Half an hour later, a crowd gathered at the reservoir. Apparently, a group of teenagers went for a swim in the reservoir, but one of them was bitten in the leg by something, then another was pulled down under, with blood oozing to the surface, the teens got out of the water just in time, until, what they described as a small head attached to a long neck shot up out of the water and tried to take another one of them down, only for it to rip the left flank of a stallion and swallow it whole. The pegasus tried to generate a tornado to try and funnel out the water, but every time they fly down close to the water, the creature inside would spring up and foil every attempt to create a tornado. When Twilight and her friends arrived, the creature leapt up high, revealing what it is after nearly clipping a pegasus mare's wing with its toothy jaws.

Rainbow Dash knew who the mare was and was about to try and give the creature a beating, until Twilight stopped her, saying, "Rainbow Dash! You should have learned by now that attacking something bigger than yourself is a bad idea!"

Fluttershy asked her alicorn friend, "Uh, T-Twilight? W-what was that creature? It looked so scary…"

Twilight remembered the shape of the creature as it leapt for the pegasus, (who happened to be Fleetfoot of the Wonderbolts). It had a small head with conical teeth pointed forwards, a long neck that made up most of its upper body length. Though these traits seemed to peg this creature as a sea serpent, but the neck was attached to a wide body and two pairs of flippers, two in front and two behind, and the body ended in a stubby little tail. It was clear that the creature was from the group of reptiles called the plesiosaurs, using that knowledge as a guide, Twilight was able to identify the species of plesiosaur, it was a breed of Elasmosaurus from the inland sea that once flooded the great plains of the Mid-United States, where the state of Kansas will one day stand.

The massive reptile was an astonishing forty-nine feet in length, and weighed below three tons. The Elasmosaurus was confused and scared that it was in unfamiliar territory, and far from the ocean, so it bitterly retaliated against any perceived threat, the dinosaurs that remained behind used the reservoir as a watering hole, but they, mostly the Allosaurus, were met with the incredibly painful bites of the Elasmosaurus, who is too afraid to leave the reservoir on its own. Fluttershy knew a confused and frightened animal when she sees one, and told Twilight and the others that crucial fact that would avoid a misunderstanding…

After a while, they came up with a plan to handle the Elasmosaurus, with Fluttershy first attempting to calm the sea reptile.

Fluttershy said to the confused animal in a motherly voice, "Shh-Shh-shhh…It's okay…it's okay…we're not going to hurt you, we are going to help…YIIIEEEE!"

Fluttershy yipped in surprise as the Elasmosaurus lunged at her, its teeth barely scratched the pegasus as she dodged at the last minute. The plesiosaur hissed as a warning, though it sounded more like a growl than a hiss.

Twilight asked Fluttershy, "What did the Elasmosaurus say Fluttershy?"

Fluttershy shrugged as she said, "I don't know, I have no clue what this creature is saying, his language is unknown to me…"

That was really bad news, if Fluttershy couldn't translate the language of the plesiosaur, then there's almost no hope in getting the sea reptile out of the water. But, Twilight realized something, that the Elasmosaurus wasn't a dinosaur, it was something the author of the Dinosaur Codex called a 'marine reptile'.

She thought, Hmm…I wonder…if this creature isn't a dinosaur, then maybe…

Twilight walked up to the dangerous sea predator as it lunged at the alicorn, but was stopped because Twilight was just an inch out of range. Twilight's horn gathered magical energy as she hoped her suspicions were correct, and then, she cast a sleeping spell on the giant animal. The animal resisted, like the dinosaurs, but then, the Elasmosaurus slowly succumbed to the dreariness the sleep spell caused.

Twilight shouted, "Yes! I knew it would work! Though, not as quickly as I hoped, but, it worked nonetheless!"

She noticed the ponies staring at her, faces all saying 'what-worked' on them.

She sheepishly laughed as she said, "Um…W-well, I suspected that magic might work better on this Elasmosaurus, since the Dinosaur Codex stated that dinosaurs had a strong resistance to magic. I figured magic might work since the Codex said that it was ONLY dinosaurs that resisted magic, so…well, you got the picture…"

Now, they readied to transport the massive reptile, until the ambassadors had received an urgent message, that the magical barrier that protected the undersea kingdom is weakening, and thousands of sea reptiles and prehistoric carnivorous fish are starting to swarm dangerously close to the borders.

"…And unfortunately, only alicorn magic can re-strengthen the magic barrier, the way the merponies did it was lost thousands of years ago. We seek the assistance of Princess Celestia, to come as urgently to the Barrier's Core and strengthen it, the barrier can only hold on for so long, that is what the message said, your majesty…"

Celestia was deeply troubled, the volcanic eruption had certainly left its mark on the world, and these earthquakes are greatly disrupting their peaceful way of life. The dinosaurs, and creatures they lived with, have turned everyday into either a bloodbath, a battleground, or a life-or-death gamble. She did not want the merponies to perish at the hands of the dangerous monsters of the deep, of either natives of Equus, or visitors of this planet known as "Earth".

But, she cannot leave to prevent a terrible loss, Celestia knew she had to remain in her temporary home, at Twilight's Castle, to help coordinate stabilizing the aftermaths of several natural disasters. Celestia also knew Luna is in a similar boat, and learned that Luna lacked the experience to do what she was asked to do. Discord vanished and is nowhere to be found, saying that he, 'was going to investigate a series of disappearances happening all over Equus', so he's out of the picture…

Then, it came to her...

She said to the only other alicorn here, "Twilight, you and your friends must go. With the Rainbow Power, you can strengthen the magic barrier for it to last for a long time, until we can think of a permanent solution."

That made the six ponies say at once, "WHAT?!"

"You cannot be serious? No disrespect, princess…" Rainbow Dash said, rather skeptically.

Rarity added, "I, for one, have to agree with Rainbow Dash. What I don't understand is why?"

Princess Celestia smiled just a little as she explained, "Well, the magic barrier that protects the merponies' kingdom from many of the dangerous sea life for thousands of years, recently, it was powered by alicorn magic due to the means for them to create their own barrier was lost to the ravages of time. You can go there and power their barrier, while returning this, 'Elasmosaurus' to the ocean."

Twilight nodded, "Certainly, but…what about…"

After a lengthy train ride, with one train car filled with water for the Elasmosaurus, the group of friends had arrived at the shoreline of the Equestrian Sea. Not there for five seconds, and already, many shoreline animals of the Mesozoic Era litter the beach. Including two carnivores called Eustreptospondylus, fighting over the rotting remains of a washed-up shark. The Elasmosaurus woke up, then crawled to the ocean, hissing menacingly at some of the smaller dinosaurs that walk too close to it. The ponies glanced over to their left, and saw a strange creature perched on a rocky outcrop further into the ocean, they saw it eating a large shark, and then it…breathed steam?!

The creature was a marine dragon that lived on Earth in the Cretaceous, when the creature was visited by the blue pegasus, Rainbow Dash, it hissed then dragged the shark corpse into the water and swam further up the coastline, to feed elsewhere. The Elasmosaurus got into the water and was then greeted by other Elasmosaurus who were its family, and after the reunion, the family of sea reptiles dove under the waves and swam for the open waters, where food is plentiful, but where many dangerous predators are at their most deadly.

Twilight called to her friends and began to explain their plan once more.

"Alright girls, we know what the plan is right?"

The other five responded at the same time with a "Mmm-hmm", as Twilight went over it one more time.

"Here it is, as simple as it sounds, this is very complicated. We were tasked to use the Rainbow Power to strengthen the barrier surrounding the Merponies' capital city, despite that, the ocean surrounding the city is filled with lots of aggressive marine animals that are confirmed to be from wherever the dinosaurs were coming from. And this report delivered to us from a therapist from Manehatten from a survivor of a shipwreck merits extreme caution. Turns out, there are enormous carnivorous reptiles from the world of dinosaurs that are powerful enough to tear not only ships, but sea serpents and sharks apart as well."

Twilight took a deep breath to calm her nerves, having read about the sea monsters that lived alongside the dinosaurs greatly unnerved her, since the Dinosaur Codex said that many of these creatures are so terrifying that some make even the Tyrannosaurus look mellow in comparison. Twilight focused all her energy to this special spell Celestia had just taught her, because many of these creatures attack anything at the surface, actually walking on the ocean floor was a better option, in case the gang needed to run away. The gang huddled around Twilight as she cast the spell, a blinding light engulfed them then tightened into the shapes of each pony, then the light vanished, the spell was complete.

Applejack looked around, then asked, "Did it work? 'Cause I don't feel any different…"

The others agreed, until Twilight said, "We will know if the spell worked if we…*gulp*…g-go…in the water…"

The way Twilight answered the question unsettled the others, something is making their friend quite hesitant to even touch the sea water. Within a few minutes, they all had enough courage to head into the sea, fully aware of how dangerous it could be now, as the water parted, then formed an air bubble around them as the head deeper under the waves…

In the ocean, not far from the underwater city, a lone merpony was swimming around cautiously, looking for signs that 'it' is coming back at another attempt to devour the citizens.

They couldn't see it very well in the dark depths from when it first attempted to get inside the city nearly four months ago, they all saw the light from the city cast ominous shadows, showing a silhouette of a whale-sized monster with jaws big enough to swallow a large shark whole. When the creature charged, the barrier reflected the beast, and gave the merponies a nightmarish clear view of the monster's head, a fourteen-point-five foot long skull with huge teeth and a gigantic mouth with around seventy of those teeth top to bottom. It let out a hauntingly mellow call, then retreated into the murky waters, such an encounter terrified everyone in the city, especially when more and more of these creatures started to swarm around the city, drawn by the light of the kingdom.

Now, with the barrier starting to weaken, many prehistoric sea animals are starting to swarm the surrounding area of the boarders, mostly were assortments of fish and Coelacanths and a shark called Hybodus, a pod of Icthyosaurus and Cryptoclidus scooping up lots of fish. The merpony swam further and further away from the boarders of the city, but then, something brushed against her back, she noted it felt like sandpaper. Her eyes widened, that feeling was the skin of a shark she felt, the merpony's head ducked just in time as a massive shark tried to rip her apart. The shark resembled a Great White Shark that was striped like a tiger, it was the twenty five foot long Squalicorax, a massive prehistoric shark of the ancient inland sea that split North America in half.

The merpony dodged the carnivorous advances of the giant shark. Its teeth snapped shut on the tip of her tail fin. She past the boarders as her tail fin was getting deeper into the shark's jaws, the weakened barrier had enough magic to repel the shark as the magical shockwaves electrocuted the Squalicorax into a state of paralysis. That makes the predator a big target, as Hybodus and a hideous giant fish called Xiphactinus started to swarm around the shark, they only had a bite or two, until the Hybodus fled like minnows.

That made the merponies looking on worry, they know that fish have an innate ability to sense changes in the water, then they heard monstrous growls in the water. In an instant, two large lizard-shaped creatures swam with frightening speed and devoured their prey, one swallowed the now dead Squalicorax in one massive bite, the other bit the hideous Xiphactinus in two and swallowed the half with the prehistoric fish's head as the tail sank to the sea floor, as small sharks swam to it by the smell of blood.

The merponies panicked, these two creatures are bigger than the monster that one they remember, more in terms of length, these sea lizards are large, where one was forty-three feet long, the other was bigger, close to fifty-six feet long. The merponies at the gate looked straight into the eye of the massive sea reptile, at it stared right back. These were mosasaurs of the Late Cretaceous, their closest living relatives are monitor lizards, like the Komodo Dragon, but to the merponies they were like monstrous sea serpents. The mosasaurs swam to enormous shadowy figures swimming east of the city with numerous sharks following, for the sharks knew these creatures could leave a feast of leftovers from their kills…

"Wowie-wow-WOW! Look at that! Look at this! Ooo! Shiny!"

Pinkie Pie zipped from place to place in the sea.

They are twenty miles from the merpony's city, where the Barrier's core is located, and are currently three-hundred feet below sea level. The six friends were fascinated that they were deep underwater, seeing all kinds of sea animals from Equus' and Earth's, various fish and strange creatures that looked like octopi, but it is inside a spiral shell.

Twilight said with wonder, "Amazing…those are what ammonites look like? So interesting, their spiral-shaped shells must serve as protection from larger predators…Like that creature…"

Then they saw a small dolphin-like creature trying to bite an ammonite that retreated into the shell. The animal had the tail of a fish, a beak of teeth, and real enormous eyes.

Twilight wondered, then pulled out one of the books and searched through, "Ah…It is an icthyosaur called Olthamosaurus, and judging from the overall size and the data here, it must be a young one, possibly around two weeks old."

Fluttershy's eyes widened as she asked, "So…it's a baby?!"

Twilight answered as the Olthalmosaurus swam up in her face, "Yes, it is a baby…a very cute one at that…"

The infant Olthalmosaurus, we will call him Ivan, swam with amazing speed to the surface as a large Sand Tiger Shark quickly darted to where he was, then swam slowly as it continued its hunt for prey in the coral reefs.

Applejack shuddered as she said, "Gueh…sharks still give me the willies, especially hearin' all those stories of them attacking pony folk…"

Rarity added, "I as well, that shark's mouth was downright nerve wracking with all those teeth, I'd say it should really see an orthodontist about that."

Rainbow was the closest to the Sand Tiger Shark as it swam past them, and said, "Yeah yeah, sharks are scary, but remember this, there's something down here that attacks ships, sharks, and whales for Celestia's sake…And that book says that there were creatures more terrifying than that freaking T. rex, enough so that it said one place was nicknamed 'Hell's Aquarium' for crying out loud!"

"Dash has a point…"

Twilight said, "…So we should keep an eye out for danger, it will take a day for us to get to the city. Celestia didn't want to risk us being anywhere close to the surface due to the attacks of these prehistoric sea reptiles attacking anything they see or smell or…"

"Smell? How can they 'smell' underwater, Twilight?" Applejack asked.

"Easy…through inmernal nostrils from what the bookie-book says, silly…"

Pinkie said as Twilight corrected, "In-ter-nal, Pinkie…"

The band of six continued as they encountered more sea life, ranging from cuttlefish, plesiosaurs, icthyosaurs, a sea bird called Hesperornis, sea turtles, sea snakes, and thousands upon thousands of fish, many of which haven't been documented in science before. They continued until nightfall where before they fell asleep, they saw crawling in the moonlight on the ocean floor, a large number of strange ancient creatures heading for the shores, that have not changed for millions of years, the Horseshoe Crab.

Native to both Equus and Earth, these creatures are more related to spiders than crabs, and appeared from a time long before the first dinosaurs appeared, and still to this day, walk upon the shores of the modern world, and their world, doing the same thing their ancestors did, millions of years before…

As the night continued on down south miles from Horseshoe Bay, many microscopic organisms, like algae and plankton, swarm the water just below the surface, and attracting all kinds of sea animals, big and small. Entire food chains become more active at night, where food is everywhere, and when the Olthalmosaurus' notable feature is at its best and most affective. The iconic large eyes of these reptiles allow them to see extremely well in the dimly lit waters, the light-sensitive eyes allow these Olthalmosaurus to snap up squid in the murky depths.

Unlike their young, the Olthalmosaurus don't have visible teeth, instead, they had toothless beaks that are streamlined, and catch prey like a spring clamp. One merpony was watching them effortlessly snatch up squid after fish after squid, he couldn't help but think that the icthyosaurs were more violent versions of dolphins. He then saw a large school of fish swimming and scattering as a family of plesiosaurs, called Futabusaurus, catch one, two, three, even four fish in mere seconds.

Compared to the thousands of fish, it was an acceptable loss, for Futabusaurus were expert fish catchers, native to the seas of where Japan will be, these twenty-foot long reptiles were able to devour slippery fish with a few trademarks of the plesiosaurs, four-flippered limbs for nearly unrivaled speed and agility, and forward pointing teeth in a curved, conical shape. To the merpony, compared to the Elasmosaurus and Cryptoclidus, the Futabusaurus were more cute and cuddly than most sea reptiles.

Two of the younger Futabusaurus swam around the merpony in curiosity, and their mother swam up to him for a closer look. Her gaze turned right and down when she saw a large shadow swimming below, and sharks scattering in a fishy-panic. Other animals then felt a change in the water flow, and many of the larger ones swam quickly to the shallows, it made the merpony nervous.

He said to himself, "Knowing that they swam in a panic is not a good sign…"

He had no clue that he had actually placed himself in a very vulnerable position, one that this predator can exploit perfectly. The merpony didn't see it coming, when something big rammed his rib-cage, and left him temporally stunned, he shook his head and then saw a massive monstrous reptile with a massive set of jaws charging him.

His panic gauge shot up and skyrocketed to new heights as he swam with amazing speed for the shallows, thinking those other animals knew exactly what would keep it at bay. He turned his head behind and saw the monster closing the distance with frightening speed. The creature was a member of a group of Jurassic sea reptiles called the pliosaurs, and it was the same one that attacked the pirate ship several weeks ago. The pliosaur was close to fifty-feet long, and unfortunately, was faster than the merpony by a fraction of a mile, and thanks to its method of movement, was using less energy to swim than its panicking prey.

The merpony had never been so scared to die in his whole life, he had frequent run ins with Tiger Sharks, Hammerheads, even the Great White Sharks, but they were minnows compared to this pliosaur. He was just sixty-feet from the shoreline that bordered the shallows, he was tiring out, his muscles begged him to stop, but he knew if he slowed down for even a millisecond, he will be at the mercy of this merciless predator.

Now closing in to being fifteen feet from the safety of the shallows, he dared to look behind and saw the short tail of the pliosaur dive, then in mere seconds, he felt his tail being pulled up, then a searing pain coursed through his body. He looked behind and to his absolute fear, his entire tail fin was bitten clean off, with a cloud of blood, his blood, mucking the water from his wound. He saw the shadow of his massive pursuer swim the opposite way, then turn around for the kill.

Now desperate, he used his hooves to swim to the shallows, with his blood and movements attracting large numbers of sharks, knowing an injured animal in distress means a quick, easy meal. But were shooed away by the much larger pliosaur coming closer.

The merpony said with fear, "No! No! No! I…I don't want to die! I DON'T WANT TO DIE!"

At this point, he was practically crying as he was now, in his desperation, was just five feet from the shallows, he had hope, but the pliosaur was much too close for there to be any. He looked to his side and saw the tip of the pliosaur's enormous head starting to get ahead of him, and with a swift jerk to the merpony, the pliosaur clamped its strong jaws on his left hoof, and then jerked its head down, ripping the merpony's leg clean off.

The pain was unbearable as the force of the attack and the water displacement the pliosaur generated, shot the merpony forward, he was just a foot and a half from the shallows. He tried to move, but his body wouldn't budge, he was going into shock, a dire condition for any sea creature to be in, as he started to sink, he mustered enough strength to look under his stomach and saw the monstrous animal ready for the final strike. His hopes were gone, he's helpless now, he done everything he could to survive, but now he will be the snack of a monster. He closed his eyes and prayed his death would be quick and painless…

But then, he felt hooves wrap around him and saw two other merponies grab hold of his paralyzed body, and swim to the shallows, just as the pliosaur had all three within its jaws, the sandy bank forced them shut as the merponies made it out alive, they made it to the safety of the shallows. The water was too low for the behemoth reptile to squeeze through, and as such, abandoned the chase, and retreated to the deep waters, for easier prey like whales…

It was a monster man had discovered recently, one that had another name, once upon a time…

The Mane Six awake in the morning, and were greeted by a pod of playful dolphins and sea lions as they headed out for the capital, being over halfway there.

After a half-hour of walking, the six friends had entered the borderlands that separate the reef and the deep ocean waters, even though it was daylight, the open waters were a musky darkness, that gave an overwhelming sense of dread. Nothing was out there in the borderlands or open sea, outside of a pod of singing Humpback Whales, and another pod of icthyosaurs called Shonisaurus in the distance. They treaded through the empty sea floor and found that the lack of even a single fish quite creepy.

"It is real quiet y'all…" Applejack said observantly.

Rainbow Dash finished, "Yeah…a little too quiet…"

Twilight sighed as she said, "I'm really sorry that we had to take this route girls. According to Princess Celestia, for us to not attract too much attention, we had to tread through these waters, because the coral reef was too closely packed for us pony-folk to cross. If that wasn't the case, we would be there in an hour or…so…"

She trailed off when all six saw a huge silhouette lying on the ocean floor. As they walked closer, their faces turned pale as they saw the bodies of a dead whale and a sea serpent lying there, with hagfish and a number of crustaceans, barnacles, and other sea floor scavengers swarming all over the bodies. The whale and sea serpent had one thing in common, they were killed by an animal that bit both of them in half.

Fluttershy teared up that a peaceful and gentle creature like a whale was violently killed, she said, "W-wh-what could do something so horrible to a nice whale…?"

Pinkie looked on the body of the dead sea serpent and then said, "Twilight? What is that thing? Sticking out of the sea serpent's back…"

Twilight noticed it too, and knew immediately that it wasn't a part of the sea serpent at all, so using her magic, she grasped the mystery thing and had a little trouble pulling it, whatever it was, it was embedded deep in the creature, most likely lodged in bone. After a minute or two, Twilight succeeded in pulling the thing out in a cloud of blood, and levitated it over to get a better look, when the six saw what it was, it made them look like they saw a ghost…

The thing was a single tooth, broken off from a tremendous jerk, but it was almost a foot long, and had a design that could only mean that the owner had powerful jaws that can cut bone like a hot knife through butter.

Applejack dared to ask, "W-what kind of monster has teeth like that?!"

Twilight had seen this tooth before in the Codex, and remembering the report from the lone survivor of the attack on a pirate ship, she began to have an idea of what kind of animal this tooth belonged to. She pulled out the book she had on marine reptiles, and flipped through hundreds of prehistoric sea life, and found the tooth's owner, a species of pliosaur of the Late Jurassic called Pliosaurus funkeri, when it was first discovered by humans however, it had a different name, known as…

"Predator X…" Twilight said as she read the notes.

Rarity asked, "Twilight dear, what on earth is a…oh how did you put it…"

Pinkie jumped as she said, "She said Predator X, silly!"

Twilight nodded as she continued, "Pliosaurus funkeri, or as it was named for a time, Predator X, was undoubtedly one of the most terrifying carnivores of all time. With a staggering size range of around fifty feet, it was the top of the food chain of where an Arctic island off of Normandy will one day rise. This animal's skull alone was twice the size of the Tyrannosaurus, approximately twelve feet long, its mouth was laced with around seventy enormous teeth, and its bite is one of the most powerful in the animal kingdom, being five times the strength of that of Tyrannosaurus…"

That made their blood pressures drop, a bite that was five times more powerful than the T. rex's already massive bite, they really hope they don't run into Pliosaurus.

Twilight continued, "…My first hand experiences with these monstrous animals had made me quite afraid to step into the water for a good long while, one run in nearly cost me my life along with the life of my dearest friend. The hunting methods of Pliosaurus and its relatives was made clear in chilling fossils that were discovered, that they first attack their prey's limbs to restrict movement, and then they deal the finishing blow by attacking the head from below. This method is quite similar to modern-day sharks, particularly the Great White, and the coloring of one Pliosaurus I met had a similar color pattern of said shark. This was a camouflaging trick that ensures that in murky waters with dim lights, it couldn't really be seen above or below…"

Before anything could be said any further, a flurry of shadows belonging to a family of plesiosaurs called Kimmerosaurus soar past the six ponies like panicked birds, as the reptiles fled for the shallows.

Their sizes were massive as the six friends saw them getting further away, but Rainbow said, "Jeez, what in the hay spooked them…?"

Applejack looked in the direction they came from, her eyes were wide with panic as she said and pointed, "Uhh…m-maybe t-t-th-that!"

The other five turned and saw an enormous Pliosaurus funkeri charge with frightening speed in their direction, its huge jaws wide open.

Pinkie shouted loudly, "RUN AWAY…!"

They all started to run as fast as they could, but tripped as they held their hooves over their heads, and tightly closed their eyes as they waited for the Pliosaurus to swallow them all…

...

...

...

But, the Pliosaurus swam over their heads, the Mane Six were not its target, but the fleeing Kimmerosaurus as the monstrous animal gave chase.

They all sighed heavily with relief as Applejack said, "G-golly, I'll be havin' nightmares for weeks after that fright'ning experience…"

The others agreed as they continued to the city, now fully cautious of their surroundings, for any creature worse than the Pliosaurus, unaware that there is one sea animal worse than the most powerful monster of the Mesozoic…

Discord is in a faraway land to the east, investigating the surroundings of the entire continent because this was where his ability to sense magical imbalances were at their strongest, stronger than even after the Canterlot Eruption event.

He wore a Stetson as he said, "Aside from these new plants, nothing points to the source of that distortions I felt weeks ago. What could have caused a disturbance that strong, stronger than even that malevolent surge I felt days ago? It defies…"

His thoughts were interrupted by thunderous footsteps of something massive, Discord was then in the shadows of giants, giants of the long forgotten time. Discord gulped as he saw the heads of these giant dinosaurs look down upon him, and smelled the draconequus' scent. The dinosaurs resembled those Brachiosaurus that were in Ponyville some time ago, but bigger, much MUCH bigger. One of the larger dinosaurs bellowed loudly as the others started to move along.

Discord wiped the sweat off his brow as he said, "Well...uh...that answers that question...but, raises a few more..."

He teleported deeper into the continent as he went to see if his suspicions are correct...

At the same time, in a village far south from Equestria's borders, the villagers run in sheer panic as a wave of blood covered changelings, in a sea of ruby red blood go about drowning everything in sight, no one is safe from their summoner, the demon who has awoken from Canterlot's destruction.

The one changeling survivor hovered, turning his gaze away at his forced master's slaughter of innocents. He was utterly disgusted when the monster created a sea of blood with his victims murdering innocents.

He opened his eyes as Alastoris said, "Look my servant, part of the job requirement is to see my delicious carnage. You either watch, or your family will become my dinner, I restored your wing so you belong to…Hmm?"

Alastoris spotted a ostrich running away as his slaves try to kill it, his eyes shot open as he pulled back all of his victims to him. The changeling noticed and followed his master as he grabbed the ostrich and snapped its neck.

He asked as Alastoris tossed the dead ostrich up in the air, "S-sir…I-I-it's just a bird…why did you kill it and not just devour it, like the…others…"

Alastoris looked with a killer's intent at his servant as he unleashed an energy blast at the ostrich corpse and destroyed it.

He said ferociously, "It is a bird, they are living descendants of those cursed creatures my foes had created, millions of years ago, particularly the dromeosaurs, their blood acts as a poison to many demonic monsters of Hell."

The changeling suspected something as he said quietly, "…dinosaurs…?! What do those creatures have to do…"

The changeling was suddenly grabbed as Alastoris said with anger,

"HOW DO YOU KNOW THAT NAME! THEY DON'T EXIST IN THIS WORLD, YOUR WORLD HAS NO KNOWLEDGE OF THEIR EXISTENCE, THEY DWELLED IN ANOTHER WORLD, AND HAVE BEEN EXTINCT FOR MILLIONS OF YEARS!"

Ex-extinct?! As in…no longer alive?!, he thought...

The changeling answered meekly, "I…I…I…I heard about it from a spy of Queen Chysalis, they have appeared in all of Equestria, until these books they called recently the Dinosaur Codex arrived, no one had heard of a dinosaur until now…"

He gulped as Alastoris glared suspiciously, but let go of the changeling as he said, "Though your body language betrays someone who is lying just to save their useless hide…I know you speak the truth, you were simply intimidated…but if it is true, that dinosaurs are in Equestria, then they would spread throughout the planet…"

Alastoris heard a low, grumbling sound and saw a massive Acrocanthosaurus sniffing the air sixty feet away. It was simply looking for food, until it caught a very powerful scent that made the predator nervous. It turned its head to the demon and changeling staring right back, when the forty-foot long carnosaur saw the demon, an ancient instinctual program activated in its brain. It growled more viciously than ever before, then went into a full frontal assault to Alastoris, completely ignoring the dead and injured that remained, all it knew was that its brain told it to kill the murderous demon.

Alastoris grinned creepily as he said, "This might have been a big problem for me…"

The demon raised his hand and grasped the six ton animal in a psychic grip as he finished, "…If they haven't gone extinct sixty-five million years ago, and gave me the strength where they are nothing more than a minor setback now…"

Alastoris clasped his hand shut and crushed the poor dinosaur's neck, killing the powerful animal.

He turned to his changeling servant as he said, "If that creature was here, then there are certainly more, how many is the real question…"

He sensed for the unique signatures of non-avian dinosaurs and said, "A real hassle, hundreds of thousands of species roam the planet in numbers suitable for repopulating to sustainable numbers, to evolve…unless…"

His monstrous eyes gazed up at the stars, looking into deep space as he zeroed in on a massive shadow in front of a star that wasn't far from this solar system.

He said with an unpleasant grin as he pulled the object, "…I deny them the chance to become stronger species that could end me…a mass extinction event, of not only those accursed dinosaurs, but any other animal that will stand in my way…in a year's time…"

The changeling cowered as his master laughed psychotically, then finished, "…So long Equus, your times of peace are at their end, your times of fear and hatred…are upon you all…"

The hellish monster fired and energy blast at the Acrocanthosaurus' corpse and destroyed all but its head, as it crashed in front of one villager survivor as she screamed at the top of her lungs…

Pinkie was being Pinkie Pie being all sneaky, zipping from one place to the next, as everyone else tries to move as quietly. For the six ponies were now just seventy feet from the city, the waters surrounding the city were teeming with dangerous sea animals of the Mesozoic. Archelon, Plesiosaurus, Cryptoclidus, Xiphactinus, and Hybodus swarm the outermost borders of the city.

More dangerous sea animals swarm closer to the city, like a sea crocodile called Metriorhynchus, and a group of mosasaurs called Halisaurus, waiting for a feast of merponies and various other animals that lie in the city. The six cringed when the Xiphactinus swam beside them, they were not only huge, the fish from Hell's Aquarium were frighteningly ugly to look at.

"Yesh! That fish was cree-py!" Applejack said.

Rainbow added, "Yeah, I'll say...I don't like it at all..."

After ten minutes, the six friends made a dash for the city when the animals started to go into a feeding frenzy when the corpse of a massive Leedsichthys floated lifelessly to the ocean floor. They made it inside the city as an individual Xiphactinus tried to swallow them in a six individual bites for each of them, only for the monstrous fish to be attacked by two Halisaurus and torn to pieces.

"Boy are we happy to see you six…our princess told us you would come. Those animals are trying to get in for, obvious reasons."

Said a voice as Twilight and the gang opened their eyes.

They saw the voice belonged to a merpony guard as he helped them up...

Twilight said, "Thank you, now can you tell us where your Barrier's source is located? We're here to help you with re-strengthening it…"

"Certainly…" he began to say, "…but, you will need a member of the royal family here to unlock the Barrier's power core. It so happens that the queen is here, she can unlock it for you."

Applejack said, "Okay then, let's go and get her highness now. Something is telling me we better hurry…"

She looked up at the magic barrier, it started to flicker on and off, like a light bulb, as out of the animal feeding frenzy, massive mosasaurs looked on with predatory glares, looking at all the food around and in the city.

"I am glad you six have arrived on time…the barrier is on its last legs you see…" the Queen said to the six land dwellers.

Twilight said after bowing, "Well, Princess Celestia sent us here, thinking the magic barrier can be strengthened by a power me and my friends share, that defeated Tirek a while ago…"

The Queen interjected, "Ah! Yes, I've heard of this, 'Rainbow Power', that defeated Tirek many months ago. Does the high ruler of Equestria think it will be a viable substitute for alicorn magic?"

"She does, I also am here to let you know that our scientists are still trying to find out how the barrier was powered long ago…so far, we still have not found a solution…" Twilight said to the Queen.

The merpony ruler was frowning as she said, "That…is unfortunate to hear…"

A bunch of guards suddenly burst through as one of them said, "M-my Queen! Urgent report! A bunch of those monsters from a day ago have arrived and they broke the perimeter of the city's outlands! The Barrier's power has been drained completely!"

They all froze when a low, haunting call resonated through the castle, then the shadow of a massive, snake-shaped creature swam by the windows of the castle. Twilight noted the shape and size of the shadow and flipped through the book and found its match, utterly pale at the identity of the animal.

She said, "G-g-g-g-girls…we really need to power the barrier, like, immediately!"

Fluttershy nervously asked, "W-what for, T-Twilight?"

Twilight answered as she showed everyone the sea monster, "This is why…Tylosaurus proriger, a mosasaur of the Late Cretaceous. The apex predator of its time. The author described that these things are extraordinarily dangerous, more dangerous than any other animal of the entire planet, he or she would rather be with a pack of Tyrannosaurus or sharks than these things!"

Then a young Tylosaurus entered the castle and attacked any merponies inside. They all knew they better get started, before they become food. The mosasaur tried to eat one of the merponies, but was fended off, which frightened the youngster enough to make it cry for help, then the mother Tylosaurus came rampaging through, making short work of any defense measure used against her.

The six land dwellers and the queen hurried to the barrier's core, with numerous juvenile Tylosaurus chasing after them...

The group got away as best they could from the tylosaur juveniles, but had attracted the attention of the massive adults, unfortunately.

"Take this, sea-lizards!"

Rainbow Dash said as she managed to get a few of the massive mosasaurs trapped, for now at least...

After ducking and weaving through all the aggressive and hungry sea predators, the Mane Six and the Queen made it to the barrier generator, and the queen merpony unlocked it as an above-average sized Tylosaurus spotted them, then swam upwards to take a deep breath, then dived down to them. The seal was unlocked and they saw an orb of light that was fading slowly and surely burn out completely.

Twilight said to her friends, "Alright girls, we have to hurry, concentrate…"

They all closed their eyes and gathered the Elemental Energy within their hearts, and as the Tylosaurus closed in with jaws agape, everything, merpony or animal, was suddenly blinded by a bright light. The six transformed into their 'Rainbow Power forms' and then, a beam of rainbow energy was fired to the dying core as it regained its brilliant light, brighter than ever before in its time.

The light then became a glittering sphere and expanded away from the orb, any non-native and dangerous sea creature was purged from the city and thirty feet from the walls. The queen resealed the lock as the Tylosaurus regained its balance, it looked back at the city, staring into the eyes of the six ponies who stared back, then the gigantic mosasaur swam away, in its search for food.

Twilight and the others collapsed with exhaustion, the Tylosaurus staring at them sent shivers down their spines, and drained their energy.

Twilight said with a puff, "Phew…that was a…*huff*…close one…right girls…?"

The other five agreed and per the request of the queen merpony, rested in the city for a couple days.

There they saw more sea creatures, like a living Leedsichthys, the largest fish that ever lived, growing to be as massive as a whale. A lone Futabusaurus soared through the water like a bird of prey, snapping up fish and completely ignoring all the merponies. Then, the city is swarmed by unusual seabirds called Hesperonis, two meter long birds that adapted for underwater life like penguins. Things were finally relaxing…

If it wasn't for a dark shadow spying on them…

Alastoris grinned through the images in a mirror he created, he said, "So those are the Elements of Harmony I've heard so much about…their carriers…that Rainbow Power…? Hmm-mm-mm-mm-mm…mighty, mighty indeed…but that isn't enough…"

He held in a single hand, the skull of a royal guard with a helmet made of a tough material, then crushed it with incredible ease, then finished, "…to finish me…I should expand my horizons, then, my old foe, I shall hang your head as a trophy…when I deal with the dinosaurs…"

He looked at the sky, and said, "Dragon God…"

Author's Notes

I cannot be bothered to put down a list of prehistoric animals this time, because there are so many in this chapter, so I'll leave listing the prehistoric animals to you, and as a bonus, guess the nameless ones I put in...