"What are you talking about?" Rainbow asks skeptically as she walks over to Fluttershy.
"To prove to me that your ready to fight the Rainbow Pokemon, you've got to show me the strength of your bond with the Legendary Beasts you've caught." Fluttershy asks as she tosses the Pokeball in her hand into the air, sending her Pikachu into the battlefield.
"I'm always up for a little competition. You're on!" Rainbow says she reaches into her bag as Fluttershy explains the rules.
"In this match, you may only use the three Legendary Beasts to defeat three of my Pokemon in a single battle where anything goes." Fluttershy says as Rainbow's pulls out a Pokeball and throws it, sending Raikou out, who lands on all fours before looking back at Rainbow with a confident look on his face.
"I await your command, Mistress." A male voice says in Rainbow's mind as the thundercloud on Raikou's back begins to spark. As Rainbow's about to issue a command, Pikachu dashes forward, engulfing himself in electricity in the process. Raikou swiftly jumps out of the way as Rainbow shouts "Thunder!". Raikou roars and unleashes a massive lightning bolt, striking Pikachu in the dead center of it, blasting him backwards.
"Mistress, a word of advice." Raikou's mental voice reaches Rainbow's mind. "In battle, due to the telepathic connection between us, there is no need for words for me and my brethren. Simply think of what you want us to do and we'll do it." Raikou explains as Pikachu slowly gets up and approaches Raikou with a disoriented look on his face. Raikou's fangs then start to spark before Raikou rushes forward and clamps his jaws down on Pikachu, shocking him, before unleashing a massive explosion of electricity from the cloud on his back, knocking Pikachu unconscious.
"Good job, Rainbow!" Fluttershy says encouragingly as she returns Pikachu and pulls out another Pokeball. "Now bring out your next Beast." Fluttershy says as she throws the Pokeball, sending a Snorlax out to fight. Raikou walks over to stand behind Rainbow as Rainbow throws a ball, releasing Entei, who unleashes an earsplitting roar with flames leaping from his mouth as he lands on the ground, before spewing a massive fireball at Snorlax, which produced a star shaped explosion upon making contact. After shaking off the flames, Snorlax leaps forward and slammed belly-first into Entei, who's mouth had become engulfed in flames. As Snorlax landed, Entei clamped his flaming mouth shut on Snorlax's enormous stomach as a counterattack, before flinging Snorlax back at Fluttershy, who barely managed to dive out of the way of the creature's enormous bulk.
"Very good, Rainbow!" Fluttershy says as she gets up, panting. "But we're not finished yet!" Fluttershy yells as she climbs on top of Snorlax's stomach. "It's time for the Pulverizing Pancake!"
Fluttershy crosses her arms in front of her face and quickly brings them down to her sides, extends them out in front of her, brings both of them diagonally down to the side, and raises her other arm diagonally to the other side before making a Z with her arms. After completing the intricate manouver, a yellow aura emanates from her and enters Snorlax, causing it to glow as Fluttershy gets off of Snorlax, who looks up at Entei as his eyes glow red before performing a leap, flipping once in the air, and landing on the ground, causing the ground to shake in the process as Rainbow slowly starts to panic as Snorlax begins to run towards Entei with its arms pinwheeling.
Entei looks back at Rainbow as a new voice enters her mind and Snorlax performs a small leap. "Mistress, if I may, I think we can end this with one attack." Rainbow nods and Entei quickly looks up at Snorlax as it falls towards him, kicking its feet all the while, before a massive stream of blue flames erupts from his mouth, knocking Snorlax out of the sky and onto the ground at Entei's feet, where it collapsed into unconsciousness.
"One more left, guys!" Rainbow shouts as Fluttershy reaches into her bag and pulls out an old looking Pokeball and Entei leaps over to join Raikou. Fluttershy tosses the ball as Rainbow reaches into her bag for Suicune's Pokeball, sending Charizard into the fray. Rainbow, realizing where Fluttershy would be going with this, goes to throw the ball to send Suicune out, just as Fluttershy reaches for the bracelet with her Key Stone in it on her other arm, causing Charizard to get enveloped in a purple sphere of energy. As the sphere explodes, revealing a Mega Charizard Y, Suicune emerges on the field, and doesn't even blink as he and Rainbow begin to breath in sync and the sun began to shine brightly as the two combatants stare intensely at each other. Suddenly, a giant ball of fire emerges from Charizard's mouth and goes flying towards Suicune, only to fizzle out under a massive stream of water originating from Suicune's mouth, which continues onward and collides with Charizard. Suicune then proceeds to roar as the sky gets covered up by thick, dense clouds that quickly unleashed a pelting snowstorm on Charizard before slowly dissipating under the glaring sun as Charizard gets up and spits a massive wad of fire at Suicune. The fire hits Suicune and explodes violently upon contact, leaving Suicune Burned while Charizard attempts to catch his breath, giving Suicune the chance to finish him off with a lethal Hydro Pump. Fluttershy returns Charizard, before walking over to Rainbow and pulling a small pouch out of her bag and handing it to Rainbow.
"Congratulations, Rainbow! When we were last in Alola, I talked to Professor Kukui and to Professor Sycamore's assistants. We decided that when the time was right, I could give you this." Fluttershy says as Rainbow opens the pouch and pulls out a rainbow colored bracelet with a Key Stone in it. "That's a Mega Bracelet. I had Rarity make the bracelet for me to give to you." Flutershy says as Rainbow slips the bracelet onto her left arm before reaching into the pouch and pulling out something that looks like a purple and blue cat's eye marble. "That's a Mega Stone. Latiosite to be exact. The other types of Mega Stone are in there too, as well as a Red Orb and a Blue Orb." Fluttershy says as Rainbow sets the Latiosite aside and reaches into the pouch once more and pulls out another bracelet. "That's a Z-Ring. There's also a set of Z-Crystals in there so your Pokemon can use Z-Moves." Fluttershy says as Rainbow reaches into the pouch and pulls out a red, a blue, and a yellow Z-Crystals and sets them beside the Latiosite before placing the pouch in her bag, turning towards Entei, Raikou, and Suicune. She then proceeds too hand each one a Z-Crystal before throwing a Pokeball, letting Latios out, who she immediately gives the Latiosite to, before turning to Fluttershy and looking at the tower before them.
"Now that we're 20% cooler, it's time to take on Ho-Oh!" Rainbow says before proceeding to enter the tower with the Legendary Beasts and Fluttershy in tow.