Since the beginning of time, light and darkness have been eternal enemies. Each power representing good and evil clashed for dominion over everything that existed. One wished to bathe universes in light. The other desired all dimensions to dwell in darkness.

For billions and billions of years, they battled across the stars and through the cosmos, the fabric of reality theirs for the taking. But light cannot exist without darkness, nor the other way around. Their battle was cursed to last for eternity; to wage from the start of time to the end of all things.

Hoping to bring an end to the long war, Galeem, the embodiment of pure light, terraformed a world to make his own: the World of Light. The planet was home to a group of heroes and villains from across dimensions, fighting for both sport and the safety of their homes. They called themselves the Super Smash Brothers.

They stood no chance. They were captured by Galeem and copies of them were made to create Galeem's new army. But hope still shined. Only one of the unity survived the attack and he set out to rescue his friends from the chains wrapped around them.

His journey was long and difficult, but the sole survivor robbed Galeem of his army and defeated the celestial being in combat. Seeing his chance, Dharkon, the chaotic force of darkness, drove the weakened Galeem off and remade the world in his own image.

But the fight failed to stop there. The Smash Brothers learned of Galeem and Dharkon's conflict, gathered more of their allies, and defeated Dharkon just as they did for Galeem.

Both sides were now desperate, as a third faction neither of them anticipated threatened to undo all they had achieved. But, as fate would have it, light and dark continued to duel in an ultimate battle for the fate of not just the planet, but the multiverse itself.

In a final stand, the Smash Brothers rallied alongside the souls of the many beings Galeem and Dharkon had forced into their soldiers. They pushed through the remains of the ground forces and were granted the power of the legendary Smash Stone, a crystal created by Galeem eons ago to pump life into the multiverse like blood from a heart. With this strength, they bested both light and darkness, conquering the ancient conflict and restoring the one, true balance between both powers.

Galeem and Dharkon lay dormant, not destroyed. Their light and darkness still seep across the planet and beyond. But their threat to the world is over. There is a chance for peace.

But in this world, peace is not forever.

From the ashes of an old war, a new one is slowly igniting...

…

Two months after the Ultimate Battle, the Smashers have relocated yet again.

In the wake of Galeem's assault, their old building, Smash HQ, was left derelict and abandoned. Various trips to the headquarters had items, vehicles, and data transferred to their new hangout spot.

And where better than Galeem's old turf in the World of Light?

High over the land, Charizard swooped through the sky with mighty beats of his wings. He flew over forests and cities, gazing down at the lively inhabitants below. It was hard to believe that two months earlier, every inch of this place was patrolled by Galeem's soldiers: lifeless copies of the Smashers. Now, everywhere one would look, life flourished. Miis and Inklings coexisted in Console City, Pokémon Trainers walked the streets of Lumiose City and Pokémon of all types wandered about in the jungles, desert, ocean, and volcano. Beside them, various other creatures would frolic and roam as they pleased.

The base where Galleom was once stationed was converted into a headquarters for the Smashers. Bowser reclaimed dominion of his old Molten Fortress. Racing vehicles and an occasional blue streak sped down a track overlooking the vast, blue ocean. Donkey Kong could be seen roaming the lush jungles with his little buddy in tow. Kirby and Yoshi wandered around Ribbon Road, two Arwings soared overhead by the looming figure of the Great Fox, the Ice Climbers made themselves comfortable in the Frozen Mountain, and Pit established a stronghold in the nearby mountain temple with the goddess he dutifully served.

The Super Smash Brothers had their numbers fully restored near the end of the war, and now they stood stronger than ever. And the World of Light still had enough room for any more newcomers…

…

Eastern Town

Mario and Luigi were sitting on a bench and talking to each other while Toads, Villagers, and Miis walked the streets. Even now, the brothers still couldn't believe they had no enemies to look out for. Heck, Luigi even peeked around every corner he came across! Mario was positive that their troubles with Galeem- and Dharkon for that matter- were finally through. The brothers had nothing to be worried about…

"YEEEEEEK!"

Until now.

Mario and Luigi bolted up from their seats in alarm, the latter looking around every-which-way. Mario pinpointed where the scream had come from and he pointed down the street. "This way!" he called, taking off towards a small building. Hastily, Luigi ran after him. The two brothers ran to a greenhouse filled with flora from across worlds, where Mario shoved the door open and dashed in. A breathless Luigi followed him. The first thing the brothers saw… was a terrified Toadette and a shaking Isabelle.

"M-m-m-Miss Isabelle?" stammered Toadette. "Please tell me THAT plant wasn't on your agenda for the town!" Mario looked to the potted plant section, looking over several plants such as a pointy-edged sunflower…

...and he saw a red snapping Piranha Plant with white dots. When Luigi saw it, he jumped back in shock. Confused, Mario turned to Isabelle and Cappy blinked open his eyes. "Hey, what's going on here?" asked the hat. "Why is there a Piranha Plant in here?"

"Oh! Mario!" gasped the secretary. "I just thought this town could use a little more life, so I ordered the construction of this greenhouse with the mayor's approval. But… it seems that one of the seeds I acquired turned out to not be such a good idea after all!"

Luigi held out a finger to the carnivorous plant… and fearfully jerked it away when the plant tried to bite down. The green brother slowly backed away and held his hands out as if he was addressing an angry dog. "And… how did you get a Piranha Plant seed, of all things?" Mario backed up his buddy's question with a questioning shrug.

"A funny story, that one!" Isabelle answered. "Do you recall when Bowser Junior challenged Diddy Kong to an aerial stunt-off?" Mario put a hand to his chin, thinking for a moment. He nodded, remembering how the chimp had made the prince a total chump.

"Well, that seed managed to fall from his vehicle. I decided to not let it go to waste, so I planted and watered it. And then it grew into… that."

Luigi was now as far away from the Piranha Plant as possible, hugging the greenhouse wall. Desperately, he dove into a bush dotted with fruit to hide. And from the leaves, he stammered something out.

"Yeah, he has a point," Cappy added. "Why did Bowser Junior have that seed in the first place?" Mario spoke something else to Cappy, which made the hat's eyes widen. "Great idea! Isabelle, do you know where you last saw him?"

"Sadly, no," the dog shook her head. "But maybe… I can take care of this plant. Perhaps I can tame it to not be so mean to others… and myself." Luigi popped his head out of the bush.

"See if you can keep that promise," Cappy replied. "C'mon, Mario! We've got a mystery to crack here!" The two plumbers nodded and dashed out of the greenhouse while Isabelle and Toadette waved goodbye. "Let's-a go!"

…

The day passed on. Mario and Luigi approached anyone they saw and asked for information about Bowser Junior. But they didn't get anything good to go on. Whenever someone said a location where he was last seen, the prince was nowhere to be found when they arrived. Mario did run into some of the Koopalings, but when Cappy asked them about the seed, they had no idea what the hat was talking about… especially Morton.

The brothers were exhausted after hours after searching, with Luigi requesting a break. The duo headed over to Console City, hoping to ease their minds by sightseeing and spending time with their friends…

"MARIO! LUIGI!"

The startled brothers spun around to see Toadette running up to them. She paused in front of them, gasping for breath. "I… have been looking… for you guys… I have news!"

…

Meanwhile, in River Woods

The sounds of wildlife and trickling water filled the forest, where small creatures and Pokémon romped and frolicked around. Squirtle playfully sprayed water at an Oshawott, who jumped away. Pikachu was curled up into a yellow ball, sleeping in the rays of the sun. Ivysaur roamed about, looking to the river where Bulbasaurs were gathered.

A twig snapped in the distance. Squirtle paused his encounter with a Snivy, who darted off. Squirtle turned to the bush in curiosity and waddled up to the foliage. Something about the bush looked odd: among the green, there were hints of red and white. Squirtle crept closer to the bush…

...and he saw the red-and-white bud open up to reveal a maw of vicious-looking teeth.

"SQUUIIRRRTTLEEE!"

Pikachu was jolted awake and Ivysaur whirled his head to the scene. Both Pokémon cried out in horror when they saw Squirtle. The Water-type had retreated into his shell… which was in the jaws of a ferocious plant monster. The plant shook wildly and bit down hard on the shell, attempting to crack it like a nut. After some more shakes, it bashed the shell against the ground.

"PI-KA-CHUUU!" A stream of yellow lightning struck the plant's head. With a moan, the plant released Squirtle and slumped to the ground in pain. Squirtle popped out of his shell and made a break for it. Pikachu and Ivysaur got into defensive poses, locking their eyes on the monster.

The plant shook itself and snarled at the two Pokémon, displaying its wide jaws and sharp teeth. Pikachu saw his chance and lobbed an Electro Ball right in the mouth. The monster was stunned, but only for a short time. Ivysaur used Razor Leaf on it, dealing damage to the ferocious flora. Pikachu charged in at full speed and jumped at the plant…

...and it changed. The plant monster turned black, grew slightly larger in size, and orange spikes grew from its spots. It swung with the force of a wrecking ball, slamming Pikachu out of the way and into a tree. Ivysaur looked on in bewilderment and turned to the plant just as it reverted to normal.

Ivysaur roared and lashed out with his vines. The plant bit and chomped at them, snapping them out of the air. It drew back… and spat out a jet of flame at Ivysaur. The Grass-type Pokémon cried out and staggered back, smoke trailing off its form.

Pikachu shook his head and gasped at Ivysaur, who turned a weak eye to him. "Ivy…"

Pikachu nodded in understanding. It darted up to the plant monster and gave it another shock. It smacked Pikachu away with a leaf and transformed again; turning itself yellow with red spots. A purple mist flew out from its mouth, which Pikachu barely managed to avoid. Pikachu turned and bolted in the other direction, leaving a struggling-yet-still-able-to-battle Ivysaur to fend for himself against the plant monster.

…

"The Piranha Plant is GONE?!" Cappy repeated as Toadette flung open the doors to the greenhouse. She gave no verbal answer but pointed to the potted plant section. Out of all the plants there… one of them was missing.

"Someone must have taken it! A thief, maybe?!"

"Maybe Bowser Junior remembered the seed and came back for it," Cappy guessed. "I mean, it's the only reasonable answer. It's not like the Piranha Plant just grew legs and ran away."

"What Piranha Plant?"

Mario turned around… and saw a confused Bowser Junior right outside. "And I didn't come here for anything."

"Huh? Then how-" Cappy cut himself off. "Never mind. We've been looking for you all day! Isabelle said you had some kinda seed with you and she put it in here. It grew into a Piranha Plant and now it's missing!"

"Seed?" repeated the prince, placing a hand to his chin. "I don't… wait. Wait… oh yeah!"

"Oh yeah, what?" Cappy asked, raising a brow.

"I completely forgot about this because of all the smashing stuff, but you might wanna listen closely," Bowser Jr. started. "It was back before the Koopalings and I found our piece of the Stone…"

…

"Pika! Pika! PIKAAA!" Pikachu ran down the path leading to the structure marking a four-way intersection: the spot where Kirby fought and defeated the corrupted Mario. He looked around frantically for any sign of his pals…

…only to run right into someone's leg. Pikachu hit the ground and looked back up. "Ow!" moaned Pit. "Whoa, you look a little off. What's wrong, buddy?" By the angel's side, Kirby, Jigglypuff, the Ice Climbers, Yoshi, and Diddy Kong looked at the little Pokémon in worry.

"Pika pika pika!" came his reply. Before anyone could ask further, Pikachu took off in the opposite direction. "He sounds frightened. And that sounds like trouble," spoke Palutena from afar. "See what has him all spooked, but stay alert!"

"Roger that!" Pit called, drawing his bow. "Come on, guys!" He ran after Pikachu with Kirby, Yoshi, and Diddy right behind him. Several minutes passed until the group reached River Woods… and Pit paused, turning his face to the air.

"Do I smell… smoke? Pikachu, is there a fire?" The little Pokémon didn't stop to answer. Instead, he continued to run into the forest. Shrugging, the angel sprinted after him. And as he ran… he saw traces of destruction.

Patches of ash, cinders, and smoke from burn marks. A Koopa Troopa poked its head out of its badly-scratched shell. Three Yoshis lying on the ground in pain past the wooden bridge. Small Pokémon looking both injured and poisoned. Several Trainers were on scene, tending to the creatures while Leaf shouted orders Pit couldn't clearly hear. Even a Pikmin was face-down on the ground.

"Heeellp!" Luigi ran past the angel while screaming in terror. Near his location, Pit could hear Mario jumping about, along with someone shouting out. Was that Bowser Jr.? The angel could hear the sound of Clown Car rotors… he had to hurry!

"Careful, careful! Whoa, look out! It's fast! Don't let it-" The unknown enemy swiftly moved away from Mario, swatted him with something green, and bashed him away with its head. "Aww…"

Pit paused, getting a clear view of Bowser Junior circling a… "Is that a… Piranha Plant?"

"Not so loud!" Palutena shushed him. "She'll hear you!"

Pit was seriously confused. "Wha-"

"Did someone say Piranha Plant?"

And his heart immediately sank at a girlish tone. "Oh no…"

"I wrote my thesis on Piranha Plants!" Viridi boasted while Pit watched his friends attack the plant. "There are just so many species! You got your basic Piranha Plants, your Fire Piranha Plants, Ptooies, Nipper Plants, Nipper Spores, Munchers, Jumping Piranhas, Wild Ptooie Piranhas, Propeller Piranhas, Naval Piranhas, Chewies, Megasmilax, Piranha Pests, Piranha Sprouts, Frost Piranhas, Putrid Piranhas, Proto Piranhas, Piranhabons, Piranha Beans, Mom Piranhas, Small Piranhas, Elasto-Piranhas, Piranha Planets, Bungee Piranhas, Big Bungee Piranhas…"

Surprisingly, the flora managed to evade everyone's attacks and strike back at them. It chomped at Popo, smacked Kirby with its pot, spit poison at Yoshi, head-butted Jigglypuff, and blasted fire at a screeching Diddy. It swung its pot at Yoshi and Pikachu, kicking them both up. The Plant chomped down on them and launched them into the air.

Pit moved into position to try and get a clear shot at the plant… but a certain nature-lover kept distracting him. "...Ghosts, Nipper Dandelions, Spiny Piranhas, Dino Piranhas, Fire Stalking Piranhas, Piranha Plorps, River Piranhas, Big Piranhas, Stalking Piranhas, Big Fire Piranhas, Prickly Piranhas, Peewee Piranhas, Inky Piranhas, Gold Piranhas, Bone Piranhas, Big Bone Piranhas, Piranha Pods, Piranha Creepers, Nipper Spore Patches, Paper Fire Piranhas, Poison Piranhas, Big Poison Piranhas, Upside-Down Piranhas, Petey Piranha, Paper Petey Piranha, Petea Piranha-"

Pit cringed and knocked himself on the head. "Trying to focus here!"

She didn't seem to hear him. "I haven't even started on all the minor variations!" Pit heard her take a deep breath…

"ENOUGH, Viridi!" boomed a frustrated Palutena. "I never want to hear the word 'piranha' ever again!"

Pit sighed, silently cursing himself for thinking introducing Viridi to extradimensional flora was a good idea. "I guess this means I'm not getting any fighting tips," he moaned. "Thanks, Viridi." Readying his blades, he dashed for the plant. "Alright, you horticultural horror! You're due for a little trimming!" He swung a blade at the plant's neck…

...and the plant ducked into its pot. Pit paused at this movement, blinking in confusion. Shrugging, he gave the pot a strong kick and sent it tumbling along the grass. The pot landed on its side… and the plant lashed out with an open maw!

"YOW!" Pit yelped, raising his arms. Jaws closed around one of his blades, ensuing a wrestling struggle between the two of them. Pit tried to wrench his weapon away from the plant, grunting as he did so. "Drop it! Drop it right now! I said drop it!"

The plant's reply was throwing Pit to the ground and spitting out the blade. "Bad plant!" Pit yelled, snatching up the blade. He took a glimpse at it… and shriveled in disgust when he saw drool covering it.

A green-spotted egg bounced off the plant. It turned to Yoshi, who lobbed egg after egg at it. The Piranha Plant bit down on one of them, cracking it. It spread out its leaves, spun them around, and lifted itself into the air.

"What the-? Since when can a Piranha Plant do that?!" Pit gawked to a nervous-looking Bowser Jr. "Just this one."

"What do you mean, just this one?"

"Look, fight now, answers later!" Bowser Jr. flew in with his Clown Car and activated its claw. It snatched onto the plant's pot and lowered down to the ground. The plant lunged and snapped its jaws at Bowser Jr., who kept his distance. "Okay, okay, I get it! Here!" He reached down and tossed a small chunk of meat into the plant's mouth. The Piranha Plant munched on it, its movements starting to slow down…

...and with a big yawn, the plant slumped over and started to snore. "That meat Kamek enchanted to make it fall asleep oughta keep it busy," the prince said. "At least until I get it to know what's food and not food."

Bowser Jr. looked up and noticed everyone looking at him expectantly. "Oh. Um… okay, I suppose I should tell you all what I just told Mario a few moments ago," he began.

"Ahem. Okay, so a long time ago, my dad was understandably upset about how Mario was able to best most of his minions so easily. Goombas were flattened from a single stomp, Koopas were kicked into their comrades, and Piranha Plants were burnt by thrown fireballs.

"I had an idea for him. I told him we needed faster minions. Stronger minions. Unpredictable minions that would keep Mario and his pals guessing. Our first attempts were simple: supersizing Goombas with Mega Mushrooms. But that still wasn't enough. While they proved to shrug off one jump, consecutive stomps were enough to squash them.

"Kamek and I found a Piranha Plant seed and decided to experiment on it. With his magic and some items I swiped from anywhere in the Mushroom Kingdom, we made sure the seed would grow into the perfect biting machine."

Bowser Jr. turned the pot so everyone could see the underside. "First off, mobility. No more would the Piranha Plant stay rooted in the ground forever. We gave it these green, stubby legs to allow it to chase after its prey."

"I still can't believe it really just grew legs and ran away," Cappy added in disbelief.

"The leaves serve as a secondary means of attack, aside from an extendable stem," Bowser Jr. continued. "They can also spin like a propeller, generating enough lift for the plant to get airborne."

"A flying plant?" Pit repeated. "Wow… who would've guessed?"

"Wowie…" Luigi added.

"And now for my favorite part," Bowser Jr. spoke. "Subspecies morphing. Using the flowers and mushrooms I picked up, I allowed the plant to transform into four Piranha Plant subspecies: the Fire Piranha Plant, the Stalking Piranha Plant, the Prickly Piranha Plant, and the Putrid Piranha. A triple threat of fire, poison, and brute force with an extendable stem to back it up."

"How did you get its seed, then?" Pit asked. "Did Kamek ask you to hang on to it?"

"Uh-huh," the prince answered with a nod. "Until we were ready to proceed with growing it, I stashed it in my Clown Car for when the time was right. But then, the whole jig with the Smash Stone happened, I met all of you guys, blah blah blah, and in the end, I ended up forgetting about it until now."

"Well… it's safe to say your dad's ultimate minion plan worked," Pit finished, glancing around at the destruction. "Maybe a little too well."

"But the uncontrolled aggression might be an unintended side effect," Bowser Jr. added. "After it fled from the greenhouse, it made its way here and attacked everything that moved. Its only targets were supposed to be Mario and his friends, but now that things have changed… we might need to do some obedience training."

"Are you saying it could be Smasher material? One of us?" Cappy asked.

"Umm… possibly? I'll have to see what my dad thinks."

"And we'll have to see what we're going to do with a plant that wants to eat our faces off," Cappy added. "In the meantime, all of the Pokémon are gonna need some medical attention, as well as the rest of the animals here."

Ivysaur and Squirtle approached Pikachu, the latter pleased upon seeing them able to move. He turned to everyone else… and his ear twitched. "Pika?" He looked to the river in confusion.

"Pikachu?" Pit asked. "What is it now?" The angel tried to listen for something, but all he heard was the sound of water from the river. Except… something felt off. The sounds of water didn't sound natural. It sounded like… a boat was navigating through the river.

"Do you guys hear that?" he asked.

"Yeah, what is that?" Cappy asked. "A boat?"

Bowser Jr. scoffed. "It's probably that singing turtle again…"

"I don't hear a motor," Cappy replied. No sooner than he said that, Luigi tapped Mario's shoulder and pointed to the bridge in alarm. Mario turned around while Diddy, Kirby, and Yoshi joined him. And on the bridge, strange figures stood waiting for… something.

A Mii Brawler encased in gold had his arms crossed. A copy of Mario in red, white, and blue stood near a red-dressed Peach. A Pikachu wearing a hat sat close to a male Mii Brawler in a Smash Bros t-shirt. Nearby, a female Mii Gunner wearing a similar shirt looked at her arm cannon and tossed a Poké Ball up and down in her hand.

A big, red raft drifted into view with its four riders paddling with oars. A rope was tossed out to the gold Mii, who secured it to a tree. With a thumbs-up, he gave the crew the all-clear. The raft pulled up to the bridge and more figures, all in red, stepped out. Rosalina with a crimson Luma, Kirby, Yoshi, and Bowser.

Pit's mouth was wide open. "What… the…?"

"Are they…" Cappy whispered while Mario and Luigi looked shell-shocked. "N-no… that's impossible, we-"

The figures came together on the bridge, some of them saying words none of the Smashers could hear. The red Bowser looked around, glancing in the Smashers' direction. It turned back to its own group…

...before it jerked its head up in alarm and whirled back to the Smashers. The rest noticed this movement… and looked in the same direction.

"..."

An awkward silence befell both groups. For ten whole seconds, no one made a move, save for the occasional blinking. And then…

"GWWAAAARRRRRGH!" The Bowser puppet jabbed a clawed finger at the Smashers. The clones charged at a full sprint, the gold Mii quickly running to the front of the pack. The red Bowser puppet chucked Bob-ombs at the Smashers and the Mii Gunner threw the Poké Ball to the ground. From it, a fake Eevee sprang out and took off running close to the Pikachu puppet. The Gunner aimed her cannon at the Smashers and opened fire, letting loose a volley of lasers.

Pit barely had time to throw up his orbitars and block the lasers. Diddy flew into the air and shot the Bob-ombs with his popguns. Everyone else scrambled into position while Pit turned to Squirtle, Ivysaur, Jigglypuff, and the Ice Climbers.

"Find anyone you can and get them here fast! Go!" With those words, they took off out of the woods. Bowser Jr. released the Piranha Plant, retracted the Clown Car's claw, and let out a sharp whistle. On cue, the Plant snapped awake and snapped its jaws. It turned to the prince of the Koopas, who pointed at the approaching puppets.

"Sic 'em, boy!"

The plant complied and took off with gnashing teeth. It dashed past the Mario Brothers and pounced at the surprised Yoshi puppet with an open-wide mouth…