Prince Blueblood watched the room beyond his cell flood with writhing, grasping vines. They entwined his cell’s bars and sprouted misshapen sacs, which burst into a fine light blue mist in the prince’s face. He felt his horn tingle.
“Oh, so it’s going to be like that, is it?”
A blur of brown and gold swept past his cell, shredding the vines into pieces. Saguaro Shade stood before Blueblood, sheathing his Grandiose Gladius. He saluted.
“Sir. I’m here to rescue you.”
“I thought I made it clear that I wanted no guards to follow me down here.”
“Forgive my presumption, sir. I was under the mistaken impression that you would require assistance.”
“Well, you might as well make yourself useful. Open this door.”
Saguaro Shade bucked one of the door’s hinges. The entire door twisted off and clattered to the floor.
“Must you be so violent?” grumbled the prince. “I am trying to establish a rapport with these dogs, and you’re destroying their property.”
“Forgive my rowdiness as well, sir. Now, if you would be so kind as to follow me.”
Saguaro Shade hacked a path through the vines. The two made it to the next room, and Saguaro jammed the door shut behind them.
“This is the way out,” the commander said, trotting to a far door.
“I am not looking for a way out. I came here for information, and I will not leave until I get it.”
Saguaro Shade sighed and turned around. “Your highness-”
Blueblood was no longer there.
“How in the-”
Radish landed in a pile of loose earth, atop a pile of firm clay, atop a pile of gravel. He shook the dirt out of his mane and wiped it out of his eyes. He looked around. He was in a massive underground open space, lit by softly-glowing lamps mounted on the walls. It was a warzone.
The black vines were coming out of the walls, ceiling, and floor. Dozens of diamond dogs were fighting against them- slicing them with their claws, ripping them apart with their teeth, and skewering them with their spears. The dogs were slowly losing ground against the sheer numbers of their enemy.
Radish looked around and saw his armor lying in a heap. He redonned it, and then noticed Eddie digging at a lump in the pile. It was Timber Spruce, half-buried in the dirt. Radish pulled him out. Timber coughed up a gob of soil, then took in the scene in front of him. “Whoa.”
Radish unsheathed his sword. “Eddie, get back in my bag. Spruce, get behind cover.”
“What are you going to do?”
“I swore an oath to protect Equestria’s peoples from all opposers. Its peoples include diamond dogs, and its opposers… are everywhere.”
“You can’t win against those plants.” He gestured to the dogs. “They can’t win against those plants.”
“You’re the one who formed a symbiosis with them. You must have learned something. How do we stop them?”
Timber rubbed his head, trying to think. “I… don’t know. These plants seem to combine traits from several highly invasive species- river goatweed, rockthorn, throttling vine…”
“I know from experience that Discord is lazy. When he creates something, he cobbles it together from pre-existing things. If any of those species have notable weaknesses, they would have been cobbled in, as well.”
“Well, river goatweed dies off quickly in saline soil. Rockthorn is highly susceptible to iron poisoning. And throttling vine… uh…”
“Yes?”
“...throttling vine…”
“Come on, Spruce. You’ve got this.”
“...throttling vine has an allergic reaction to silver! It’s why they call it ‘werewolf creeper’ down south.”
“Okay. So, salt, iron, and silver.”
Several vines burst down from the ceiling, careening toward Radish and Timber. Radish readied his sword. A massive female diamond dog, white with black spots, landed in front of the ponies and seized the vines in her paws, holding them at bay.
“Ponies know how to kill vines?” she asked.
“How did you-” started Radish.
“Diamond dogs have good ears. I have been listening to ponies. You have plan or not?”
“I do,” said Timber. “Do you know where their root system is?”
“Yes! I will take you!”
She tied the vines in her paws into a knot and kicked the mass away. She faced into the chamber, arched her back, and howled. The calls echoed throughout the chamber, and several other dogs howled back. She nodded, then grabbed Radish and Timber, slung them onto her back, and leapt away. She loped down a side tunnel, carrying the ponies through several dark descending passages.
“I am Bertha,” the dog said as she ran. “I take care of diamond dogs’ food and water.”
“I’m Radish.”
“I’m Timber.”
“Good names,” Bertha said. “Very earthy.”
The end of the last tunnel terminated into a cavern split by a yawning crevasse half-filled with water. An enormous tangle of pale roots had broken through the solid rock wall and sharply angled down into the pool. It seemed to be pulsing like a heart.
“Big root is sucking up our water,” said Bertha, putting the ponies down.
“I thought so,” said Timber Spruce. “I could feel it when I was connected to them. The roots from all the vines have combined into a massive aggregate taproot. The whole system is being fed here.”
Numerous dogs were standing on the ledges of the crevasse, throwing spears at it. One leapt onto the root with a torch in his mouth, but let go with a yelp, falling down into the water below.
“It hurts to touch,” Bertha explained. “Makes paws feel like they’re on fire.”
“It looks like it’s part scorpion fern, too,” said Timber Spruce. “Scorpion fern roots have nettles that can sting you badly, even through the toughest of gloves.”
“Damn,” said Radish. “Okay, we should start by gathering-”
“Salt and iron? That’s what I was howling for,” Bertha said, gesturing behind them. Several large guard dogs had joined them from the tunnel, each carrying large wooden barrels. They put them down and popped them open- some were full of salt, and some were full of rusty iron scraps. “We just pour into the water, yes?”
“You’re okay with dumping all this in your water?” Radish asked.
“Diamond dogs will be fine,” Bertha said with a shrug. “We eat rusty nails for breakfast. With lots of salt.”
Timber nodded. The dogs kicked the open barrels into the pool.
The pool turned from blue to a mix of white and red. The massive taproot seemed to slow its pumping, then convulsed. Long cracks in the root split open lengthwise, revealing a red gooey pulp in its center. A high-pitched squeal echoed throughout the cave.
“Did that do it?” asked Radish.
Suddenly, dozens of the thorny vines burst out of the walls. Some took up defensive positions in front of the root, and some swatted at the guard dogs on the ledges, knocking several into the water. Radish dove and shoved Timber out of the way just as a thick gnarled vine slammed into the spot he had been standing. The remaining dogs piled on top of it and wrestled it down. Its tip sprouted a giant toothy flytrap mouth which snapped at Bertha. She caught its spindly teeth in her paws.
“Brown pony mentioned a third weakness!” she barked. “Use it quickly!”
“Silver!” yelled Radish. “Do you have any?”
“No silver in these mines!” she called, “Only gems!”
“Damn it,” cursed Radish. “Okay, I think I know-”
The vine threw off the rest of the guard dogs, flicking them into the crevasse. The flytrap slammed Bertha into the ceiling, then into the floor. Timber leapt behind it and put it in a chokehold. It undulated wildly in his grasp. Radish slashed it top-to-bottom with his sword. It stopped moving.
“Major, we need silver badly,” said Timber.
“I would recommend against that. Silver has been on the decline all this week.” said Prince Blueblood.
The three turned to see him standing casually at their side. Radish took a beat to recognize him. “What the? Prince Blueblood?”
“Indeed I am. I have come to-”
“Never mind!” howled Bertha. “Does fancy pony have any silver?”
“Well, of course I do!” scoffed a deeply-offended Blueblood. “My bed’s frame alone was crafted-”
“She means with you right now, sir,” said Radish through gritted teeth. “We need it to destroy all these vines, sir.”
“Ah, I see.” He held up a large silver coin stamped with a coat of arms Radish didn’t recognize. “This was gifted to me by the Tsarina of-”
“Thank you, sir!” said Radish, taking it.
“See those red fissures in the roots?” Timber said. “That’s the throttling vine’s xylem. That’s what we need to poison with the silver!”
Radish considered his options. I can’t get up to that root, and a coin isn’t made for throwing. I could stick it to the tip of my spear, but with all those vines protecting it, I’d need to make a diving spear toss through them… which I’m too bulky to pull off with enough accuracy.
“Bertha, can you throw me onto that thing?”
“Root will sting Radish,” she said, shaking her head. “Radish will fall off.”
“I can handle the pain.”
“Major,” said Timber, “you really can’t. Scorpion fern can knock an elephant out.”
“Then what do-” Radish felt a pull at his side. He looked down to see Eddie tugging his fur with a coil. Eddie pointed to himself with his tail.
“No, Eddie, you’re just an intern.”
“But ladder-backed rattlesnakes are immune to plant toxins!” said Timber Spruce. “If he can get up there, he can get the coin in the roots.”
“Okay, then, we’ve got a plan,” said Radish. “Eddie, you take the coin and climb on my spear. Bertha, you throw me over the gorge, and I’ll throw the spear at the root. Eddie will get to the finish line and stick the coin in.”
“But Radish could fall into water,” noted Bertha.
“Yeah, well, I could use a bath anyway. But I can’t swim in armor, though.”
Radish put down his weapons and took off his armor. Prince Blueblood saw his cutie mark and gasped with horror.
“You… you… how dare you!”
“What? Oh, that.”
The prince raised his hoof at Radish. “How dare you paint such filth of my aunt on your body!?”
“Sir, it’s just my-”
Blueblood swung the back of his hoof at Radish’s face. Radish leaned back, dodging it with ease.
“Stand still, miscreant!” ordered Blueblood. “You have impugned my family’s honor, and I demand satisfaction!”
“Sir! We do not have time for this!”
“Silence! I’ll have you put in the-ahhh!”
Bertha kicked Prince Blueblood over the edge of the crevasse. He plunged howling with indignation into the water below.
“Fancy pony was getting on Bertha’s nerves,” she said with a shrug.
“Mine, too. Thanks, Bertha,” said Timber Spruce, smiling up at her.
“Well, I know he can swim- he’s got like three yachts,” said Radish, looking over the cliff. “Let’s finish this.”
Eddie took the coin in his mouth and climbed onto Radish’s spear. Radish took his spear up, and Bertha picked him up and held him in her paws, getting a feel for his weight.
“Good luck, Radish pony.”
She threw Radish.
He sailed through the air, narrowly avoiding wriggling vines. One snagged his tail and held tight.
“Gah!”
He dangled upside-down, barely having managed to keep holding onto his spear. His blood rushed to his head. He looked at Eddie.
“All right, Eddie, time to bring home the silver.”
He launched his spear. The rest of the vines turned their attention to it, rushing it from all sides. Several of them grabbed it, and Eddie leapt off the spear just as the vines twisted it to pieces.
He landed on the taproot, reeled his head back, and struck forward, jamming the coin into the pulsing red tissue.
The entire root system hissed, releasing bursts of red vapor. Its surface bubbled and gray spots appeared up and down its entire length. Parts of it melted into goo and fell off, other pieces flaked away into dust.
Every vine in the room twitched violently. The whole cavern quaked, sending chunks of rocks raining down around Radish.
“Run!” he called to Timber and Bertha. The vine lost his grip on his tail, and he fell. He quickly protected his face with his hooves and plunged into the cold water.
A current swept him sideways, scraping him across one of the rocky sides of the reservoir. He felt something grab his shoulders and yank him out of the water.
He opened his eyes to find himself on a stone outcropping along the water’s edge. There was a dim tunnel entrance in the rock face leading to complete darkness. Prince Blueblood, now dripping wet, was standing at his side glaring down at him.
“Hello, your highness. I’m relieved to see you’re all right.”
“Churlish knave!” he bellowed imperiously. "I challenge you to a duel, for my family’s honor."
Radish sat up and squeezed the water out of his mane. "Prince Blueblood, we’re in the middle of a national emergency.”
“I am the nation! And you have impugned it with your vulgarity!”
“Okay, you know what? Fine. If you want to fight, I’ll oblige. But you should know that I’m the palace title holder, and I’ve had a very long day.”
Blueblood put up his dukes. “You don't frighten me. Have at you, fink!”
He took a swipe at Radish. Radish caught Blueblood’s hoof, twisted it behind his back, pinned him down, and wrapped his other hoof around the prince’s neck.
“Gaaak!”
“Give up?”
“Never!”
Radish pressed the prince’s hoof and squeezed his neck tighter.
“Urkk…”
“How about now?”
“Root? Is that you?”
Radish turned to see Saguaro Shade approaching from the tunnel. Lieutenant Scatter Shot and Marble Pie were behind him, along with several diamond dogs carrying torches.
“Hello, sir,” said Radish.
“What are you doing?” the commander asked.
“His royal highness here demanded satisfaction.”
“I see. Well, hurry up. There’s news of happenings topside.”
“We got howls from all over! Black vines are retreating!” barked one of the dogs.
“Glad to hear it.” Radish twisted Blueblood’s hoof a little more.
“Aauggh! I yield! I yield! Get off me, you brute!”
“Yes, sir.”
Radish climbed off Blueblood and extended a hoof to help him up. Blueblood rebuffed it with a harrumph and walked up to Saguaro Shade.
“Commander, when we get back to the castle, we are going to discuss that spearhorse’s future.”
“You’ll have to bring it up with your aunts, sir. They’ve been found, safe and sound.”
“Ah ha! I told you we’d have them back before supper.”
“That you did, sir.”
The group headed off down the tunnel. Radish moved alongside Scatter Shot and Marble. “It’s good to see you two all right.”
“Likewise, sir,” said Scatter Shot. Marble smiled and nodded.
One of the diamond dogs, a small brown male, leaned and whispered into Radish’s ear. “If you defeated the prince pony, does that mean you are now the prince pony?”
Radish shook his head. “No. It doesn’t work like that.”
“But your pony butt-picture shows you mounting the pony princess. It is your destiny, no?”
Marble Pie’s eyes drifted down to Radish’s cutie mark. She blushed and looked away.
“It doesn’t work like that, either,” sighed Radish.
The brown dog shook his head. “Pony butt-pictures are silly, anyway- destiny belongs in your head, not on your butt.”
“I like that,” said Radish. “Our peoples should spend time together outside of crises.”
“But ponies have crises all the time.”
“I know. But I’m working on that.”