It was an ordinary day in the Mushroom Kingdom. The clouds and hills were smiling, the various denizens were going about their daily business by collecting randomly floating coins, thus destabilizing the already-tenuous economy, and Princess Peach was in her castle and baking a cake, as is the wont of the idle nobility.
Peach started her mental timer as she put the cake in the oven. After a certain incident involving a Shy Guy gourmet, she'd gotten extremely good at counting to 30 seconds in her head, which was exactly how long it took to perfectly bake a cake. Most ovens took much longer, but Peach had access to both advanced technology and analyzed magic, both of which were combined by the Mushroom Kingdom's top techno-wizards to create the perfect cake-baking oven. It was pretty much useless for any other task, but Peach's subjects were all too happy to assist her in whatever task she desired.
Despite her frequent involuntary bouts of absence from the castle, Peach was in fact an effective ruler, as shown by her ability to keep the Mushroom Kingdom politically and economically stable despite the aforementioned randomly floating coins. She had been forced to take the throne after the Koopa Troop's first invasion had killed her mother and father, the previous King and Queen; she had chosen to retain the title of "Princess", despite technically being the highest authority in the kingdom, out of respect to her late parents.
Her ascension to the throne had come at the tender young age of 16. As she was the only child of the previous regents, she had been groomed to become the next Queen since childhood, and thus was not unused to the requisite court intrigue and political maneuvering both within the country and between the various other nations of the Mushroom World. But she was a diplomat at heart, able to gain the allegiance of former enemies and pacify feuding tribes, and her natural magical abilities let her directly help her subjects through her healing and curative arts. But her most valuable asset was not her own abilities, but those of her two most trusted allies - Mario and Luigi.
The two men had come from another world, one they called Earth, though further research suggested that they were originally born in the Mushroom Kingdom, and spirited away to Earth after the former leader of the Koopa Troop tried to kidnap them. Still, their arrival had come at a most fortunate time: Bowser, the self-appointed Demon King of the Koopas, had led a quick but brutal invasion of the Mushroom Kingdom, resulting in the death of its regent, the capture of Peach, and the transmogrification of most of its citizens into inanimate objects. The Koopas were initially interested in Peach's political power, but quickly realized that her magical talent, combined with their own dark wizardry, could create an army capable of conquering the entire world.
But from out of nowhere came two men, possessing nothing but their great leaping skills and making use of the many magical plants and fungi of the Mushroom Kingdom. Together, they had driven the Koopa armies back, assaulted their stronghold in the Dark Lands and rescued the captive Princess, all without demanding a single thing in return. And every time Peach had been captured or otherwise incapacitated, they had again and again come to her aid. Peach had bestowed great honours upon them, and they were two of the most famous individuals in the entire world - but not once had they demanded a fee for their services.
30 seconds had passed. Peach removed the cake from the oven, set it down on a plastic cake platter, and set to decorating it with white frosting and fresh strawberries. (In the aforementioned Gourmet Guy incident, she had accidentally used kitchen cleaner in lieu of frosting. That was a mistake she'd never make again.) Peach's obsession with cake was well-known among the inhabitants of the kingdom, to the point that it was rumoured that she did... rather unsavory things with cake, possibly with Mario and/or Luigi involved as well. But she had made it clear on numerous occasions that she had never been romantically involved with either of the brothers.
"Pardon me, Princess!" A castle guard, dressed in a white cloak and carrying a Gadd-designed vacuum-spear, rushed into the kitchen. "A thousand pardons, Princess, but scouts have reported an Airship armada headed toward Toad Town!"
Airships? Only one force in the entire Mushroom World could construct those. "The Koopas," Peach said. "How far away are they?"
"Approximately an hour, Your Highness," the guard said. "The Brothers have been alerted. It would be best if you went to the safe room."
After so many different attempts by Bowser to capture her, Peach had seen fit to construct a panic room in the lower levels of the palace. "I see," Peach said. "Take all necessary preventative measures."
"Of course, Your Highness." The guard rushed out of the kitchen and Peach followed, casting one last forlorn look at the delicious cake.
The safe room was protected by pretty much every countermeasure imaginable - reinforced steel walls with impact-absorbing gel between, magical and psychic wards, and more. It was also firmly anchored to the earth with Gadd-designed Immovable Rods, so it would remain in the earth even if the palace itself was taken. It also had a year's supply of food and water. Only three people in the entire world - Mario, Luigi and Peach herself - could open the door, and breaching it from the outside was nigh-impossible.
So of course, Bowser himself ripped the door right off the hinges barely half an hour after his fleet arrived.
"Bwa ha ha!" Bowser's laugh was admittedly a bit goofy, but it did nothing to alleviate the menace of a massive ox-turtle with potent physical and magical abilities holding an even larger metal door above him like a Mario Kart Grand Prix trophy. "You think something like this is gonna keep me out, Princess? You gotta do better than that to stop the King of the Koopas!"
"Protect the Princess!" The elite Mushroom Retainers immediately charged at Bowser. Their vacuum-spears were specifically designed as anti-Koopa weaponry - the spear tips were diamond-hard and impressively sharp, while the vacuum component would neutralize Bowser's famous breath. So of course, the spears bounced harmlessly off of Bowser's scaly hide, and the searing inferno of his flame breath immediately melted the vacuums. He brushed all seven Retainers away with a single sweep of his arm.
Peach was not defenseless. She had thrown down with the Koopa King before, and she'd even won once or twice. But something was... different about him this time. Though he had always been arrogant and pig-headed, he'd been mentally worn down over the years by his many defeats at the hands of the Mario Brothers. But this time, he practically radiated confidence. He seemed to be stronger than usual, too; his physical strength often varied, but he wasn't even winded by ripping off that door. His horns and teeth seemed to be longer than usual, his skin was slightly discoloured, and Peach could swear that his red eyes were glowing in the darkness.
"Oh?" Bowser said, noticing Peach's odd look. "You noticed, huh? Yeah, I bet you're thinking 'Wow, that studly final boss is somehow even greater than usual'! Well, I don't wanna spoil anything for ya, since you'll see soon enough, but I'm much stronger than before!"
As a demonstration of his new power, Bowser's ribs immediately pierced through his chest with a sickening squelch. Seemingly unconcerned with that little anatomical problem, Bowser proceeded to direct his ribs in a choreographed little sequence, moving them in time with the wiggling of his fingers.
Peach barely held back the contents of her stomach from violently exiting her mouth. "What...?" she sputtered out.
"Oh, this? It's a pretty cool trick, huh?" Bowser's ribs retracted back into his chest, and the wounds healed within seconds. "I can do other cool stuff, too. Here, watch this!" Bowser grabbed one of the unconscious Retainers in his left hand. His fingers slid underneath the Retainer's flesh, and he proceeded to drain... something from the Retainer's body, leaving him a withered, desiccated corpse.
"You monster!" Peach yelled. She let loose a torrent of magical kinetic force from her palms, enough to reduce the wall behind him to finely-ground rubble. Her offensive magic was limited, but she'd developed that spell specifically to topple Bowser over... and it had had absolutely no effect.
"I'm just no-selling everything today, huh?" Bowser said nonchalantly. "So, Princess, you've got two choices. You can come with me willingly, or I can take you by force. I'd prefer not to harm your delicate little body, but you know I don't mind being a bit rough."
Peach responded by creating a ball of dazzling white light in her hand. She threw it directly in Bowser's face while shielding her own eyes... and to her surprise, Bowser screamed in bloodcurdling agony and fell to the ground, clutching his lacerated face.
Huh? That was purely a diversion, meant to blind a potential attacker long enough for Peach to run for it. It shouldn't have done any actual physical damage. Still, she couldn't let an opportunity like that go to waste. Peach immediately booked it up the stairs, climbing over the fallen castle guards.
"AAARGH! YOU'LL PAY FOR THAT!" Bowser lashed out in blind rage, his horns and the spikes on the back of his shell shooting out and retracting randomly. Not wanting to witness any more of his new powers, Peach threw another dazzling ball into the basement, prompting another scream of inarticulate anguish. She climbed the stairs as quickly as she could in her fancy shoes and dress, and emerged on what could only be described as a war zone.
The upper floors of the palace were ruined, almost beyond repair. The few guards remaining were fighting a losing fight against Bowser's elite troops: Koopatrols decked out in black armor, Weapon Bros. wielding hammers, boomerangs and fire flowers, Lakitus throwing Spinies from above, Magikoopas throwing spells all around, and others. But like Bowser, they were somehow different. They seemed bestial, more feral than the elite trained soldiers Peach had seen before. And it seemed that like Bowser, they were somehow feeding on her troops, as their withered remains littered the ground floor.
Peach threw another large dazzling ball into the melee. She prepared herself for a deafening scream, but none came; once the light cleared, she saw that all of Bowser's forces had been reduced to ash.
"Princess!" one of the guards shouted. Only three guards remained, and they immediately gathered around Peach. They were all badly injured, but Peach's healing magic easily patched them up.
"It... it was horrible..." one of the guards said, visibly quivering. "They're... they're stronger than they usually are. And they..."
"They ate the other guards," the second guard said. "But not with their mouths. With their hands. They just... sucked the life right out of them."
"Bowser did something similar," Peach said. Over the years, she had been in some rough situations, but she'd learned how to remain calm and composed no matter what was happening internally. She likened it to flipping a mental switch: turn the bad thoughts off for a while, at least until she was reasonably sure she was out of life-threatening danger. "At the very least, they seem to be weak to bright light."
Peach and the three guards ran outside, into the courtyard and the midday sun. Dozens of Airships were circling around the castle like hungry Cheep-Cheeps, casting the entire castle grounds in shadow. That was no doubt intentional by the Koopa King – if he and his soldiers were harmed by magical light, they'd likely be harmed by sunlight as well.
"PEEEEEEACH!" Bowser screamed. He smashed through the castle's front door, angrier than ever. His wounds had again healed, but Peach wasted no time in throwing another dazzling ball in his direction. This time, he countered with a spell of his own, a ball of darkness that neutralized its counterpart on contact.
"Bowser, what's happened to you?" Peach said. "You're not well! Whatever you've done to yourself, your soldiers, you need to reverse it!"
"Reverse it? Are you kidding?" Bowser said. "Why would I want to reverse such a wonderful gift? I haven't even shown you my ultimate technique!"
Bowser pointed both of his arms forward, and another bone-crunching sound suggested to Peach that he had dislocated them from the elbow down. His right arm began to spin clockwise, while his left spun counter-clockwise, both at incredibly high speeds, generating a whirling vortex in the middle.
"I call this one the Koopa Sandstorm!" Bowser slightly bent his arms outward, firing the vortex as a deadly tornado right at Peach and the guards. She and two of the guards managed to roll out of the way in time, but the third guard was not so lucky; when the tornado receded, there was barely anything left of the poor man.
"Now, Princess!" Bowser said again. "Wanna come with me willingly, or do you want a taste of my Koopa Sandstorm? You're a pretty tough girl, so I know you'll survive it!"
Peach bowed her head. "Promise to leave the rest of the Mushroom Kingdom unharmed. Then I'll go with you."
"You got it!" Bowser said. "I couldn't care less about your dumb kingdom! All I want is you, an eternal bride to go with my soon-to-be eternal dominion over the entire world!"
Peach slowly walked over to the Koopa King, who was now engaging in a healthy bout of maniacal laughter. Bowser was just as likely to renege on a promise as he was to keep his word - but at this point, she could at least delay him from killing more of her people. Plus, she could learn just how he gained his new power, as well as how to properly defeat him.
"Yep, it's gonna be great! Just you and me, with nothing but tim-" Bowser's gloating was interrupted by a fireball to the face. He wasn't expecting the attack, and thus went flying head-over-tail across the ruined courtyard.
"Heya, Princess!" Mario shouted as he leapt clear over the palace's outer walls. His clothes bore the distinctive red-and-white colours of a Fire Flower (a side effect of using magical items in the first place; the Mushroom Kingdom's top techno-wizards had researched it, but had ended up dismissing it as 'weird magic shit'). A few surviving Koopa soldiers ran out of the ruined door, but Mario threw several fireballs at them, immolating all of them in a few seconds.
"Sorry we're late!" Luigi said, also bearing the colours of a Fire Flower. The two Mario Brothers stood together and created a giant fireball, which they threw at the Koopa King and knocked him back through a wall and back into the castle. "Maybe it's just me, but does Bowser look different than usual?"
"Yeah, he does," Mario said. "Are you alright, Princess?"
"Yes, I'm fine," Peach said. "But be careful! Bowser's done something to his body. He has strange new powers!"
As if on cue, Bowser jumped back through the wall, his arms dislocated and preparing another devastating tornado attack. Mario approached him head-on, throwing fireballs all the way, while Luigi snuck around back. Mario's patented jump let him dodge the Koopa Sandstorm with ease, at the same time letting him get close enough for another point-blank fireball to the face. Luigi followed up with a mega punch that popped Bowser into the air, and Peach took the opportunity to throw another dazzling ball at him, scorching his feet, legs and tail with bright light.
"Whoa!" Luigi said in surprise as he barely looked away from the flash in time. "I didn't know you could do that, Princess!"
"It's not supposed to be an offensive technique, but whatever Bowser did, he seems to be hurt by it!" Peach exposited.
"Hurt by light, huh? Think Bowser turned into a vampire?" Mario asked.
"Huh? Bro, vampires aren't real," Luigi said flatly. "Then again, I've seen stranger things in the Mushroom Kingdom…"
Bowser's body fell to the ground. Both the Brothers' fire and Peach's light had taken their toll on him, and while he was temporarily incapacitated, he was quickly regenerating from his injuries.
"Princess, we should leave him to the Brothers," one of the guards said.
"I dunno about that, paisano," Mario said. "We all know how tenacious Bowser is, and that light spell the Princess has seemed to hurt him the most."
"I agree," Peach said. She readied another dazzling ball, but with surprising agility, Bowser leapt from a prone position all the way up to one of the circling Airships. Peach and the Brothers threw fire and light at the retreating Koopa King, but the Airship's hull withstood their assault.
"Give me a lift, Bro!" Luigi said. He climbed up on Mario's head as they prepared to execute a Double Jump, hopefully giving him enough lift to reach the Airship above - but before they could lift off, the castle's outer gate burst open, and a horde of zombie Koopa Troops, supplemented by zombie Toads, shambled into the palace grounds. Peach prepared another dazzling ball, but she generated little more than a few sparks between her palms; her FP pool was entirely drained, and her collection of Syrups had likely been destroyed in the crossfire. Compounding their problems was the cannonball barrage raining down from above.
"This doesn't look good." Mario muttered. "Sorry Princess, but I gotta do something you're not gonna like..."
"I won't retreat!" Peach said. "If I have to give my life to save my kingdom, I'll gladly do it!"
"Trust me, I know. But sometimes you gotta run away to prepare to fight another day." With a deft sleight of hand, Mario grabbed a small blue Mini Mushroom from his pocket and shoved it into Peach's mouth, shrinking her down to the size of a doll.
Peach impotently squeaked at Mario, and though she was too small for him to make out the words, he read her intent just fine. He gently picked her up, and with a remorseful look on his face, he muttered "Good luck, Princess." He summoned all the strength he had and threw Peach clear over the palace walls, clear over Toad Town, clear over the countryside...