The train arrives in Ponyville and Applejack and Rodan are greeted by their friends. Rodan says he had a great time in Appleloosa and asks if anything interesting happened in Ponyville. Rarity and Anguirus awkwardly shrug, because they agreed to never bring up the baby Destroyah incident again. Rodan is shocked to see Destroyah calmly allowing the Cutie Mark Crusaders to ride on her, and Anguirus admits that as long as she's with them, she's peaceful. Rarity takes Rodan aside and apologizes in advance before counting down from 3. Right on time, Rainbow Dash arrives and challenges him to a race. She claims it's to make sure he can keep up with her in the airshow. Rarity tries to mention she's really scared Rodan is faster than her, but is shushed. Rodan accepts the challenge.
A few minutes later, a crowd gathers on a hill at the edge of Ponyville. Rarity shows Rodan a map and goes over the rules. They will first cross White Tail Wood, then Big Smokey Mountain, then Canterlot Mountain, then Foal Mountain, then back to this hill. Whoever returns first and crosses the finish line wins. Of course, Scootaloo cheers for Rainbow Dash, while Anguirus is sure Rodan will win. Pinkie Pie freaks Anguirus out by doing an Eye Pop, shocked that anypony would dare say Rainbow Dash could possibly be beaten in a contest of speed. She bets Anguirus some cupcakes and bits that their respective friend will win. Rarity fires a party cannon to trigger the race and they are off.
In White Tail Wood, several ponies including Apple Fritter perform the Running of the Leaves. They are shocked when the duo speeds overhead, creating a sonic boom that knocks away a majority of the leaves. As they approach Big Smokey Mountain, Rainbow shows off by flying backwards without losing speed, but Rodan demonstrates he can do the same thing. They both speed up to about 3000 kilometers per hour. Rodan starts to lose energy because of the cold air, but he gets an idea and stops streamlining his body. He slows down for a few seconds, but the air friction is able to generate enough heat to restore his strength, allowing him to accelerate and pass Rainbow. She decides to kick it up a notch.
They pass by a weather factory from Cloudsdale, which briefly confuses Rodan, then both of them stop in confusion when they see a dark cloud with a face. It starts talking to them, demanding they get out of its way. It then attacks them with lightning, and as they dodge, Rainbow remembers she's encountered this before. She explains that Cloud Gremlins are creatures that hijack clouds and fill them with dark magic so that they block out the sun and deliver a rain that literally fills everypony with depression. Suddenly, Pinkie Pie appears out of nowhere and explains that the Cloud Gremlins they faced before came from Neigh Jersey, while these one came from the Hanc region of Prance judging by their accents. Pinkie disappears, and the two are stunned that she was able to appear in the sky, before deciding to focus on what is important.
The Cloud Gremlins move the dark cloud near the weather factory, where a hose sucks in nearby clouds for raw material. A horrified Rainbow realizes that the Cloud Gremlins are trying to get the factory to suck in their contaminated cloud, so that the factory will churn out more dark clouds. Rodan can barely comprehend what she is saying because he is ignorant about how in Equestria, ponies create the weather. Rainbow attacks the dark cloud, but she bounces off and is sent sailing until Rodan catches her. The Cloud Gremlins boast that they improved their magic so that their clouds are much denser. Rainbow tells him to go to the factory and ask them to turn the intake valves off and get everypony there to help while she keeps the Cloud Gremlins busy. Still confused, he enters the factory, but there's only one worker inside, Cloudchaser. He curses his luck.
He asks her to shut the intake valves, but she has no idea who he is and refuses to do it until she hears and then sees the battle going on outside. Rainbow repeatedly punches and tackles the dark cloud, trying to break it apart, but she's not strong enough to damage it. Cloudchaser has a little trouble with the valve's crank, so Rodan helps her turn it. He asks her if clouds here are still made of water. She asks what kind of dumb question is that, of course they are made of water, then asks why he doesn't have any feathers. Her first answer was all he needed to hear, then he flies out just in time to catch Dash after she bounced off the cloud again. She stubbornly says she doesn't need help to win, but he scolds her and reminds her that the airshow requires them to be a team. It is time to put her ego aside and work with him.
He tells her to get ready, then powers up before blasting the dark cloud with his Uranium Ray. It doesn't destroy the cloud, but the heat causes it to expand and become less dense. He stops his attack and signals Dash, who plows into the cloud and obliterates it, sending several Cloud Gremlins inside it scattering through the sky.
Rainbow says that was awesome and tries to hi-hoof him, but he doesn't understand the gesture. The celebration is short lived when Cloudchaser calls out to them and points out a dark cloud approaching that is over five times as large as the first one. From the ground, one of the Cloud Gremlins boasts that they were only the scouts and their main forces are unstoppable. Annoyed, Rodan fires a warning shot down at him and he runs away. Rainbow asks Cloudchaser where the other workers are. She explains that it is the regular workers' day off and Spitfire made Wonderbolts members like her take over for the day, but everypony else is on lunch break.
Annoyed at this news, Rainbow asks Rodan if he would be strong enough to destroy the dark cloud in his Kaiju form. He says definitely and asks her to charge him up with magic. Unfortunately, Rainbow has no idea how she was able to transform Anguirus during the fight against Garble. On to plan B. Rainbow asks Cloudchaser to steer the factory away, possibly to Cloudsdale to get help. She then tells Rodan her plan. It is time to see the true limits of their speed.
Back on the hill, everypony is excited for the race's conclusion except Destroyah, who just stares stoically. They see Rodan approaching, which shocks Scootaloo. Rodan is traveling so fast that he's creating a trail of fire. When Rarity notices he's not slowing down, she realizes something is wrong and tells everypony to hit the dirt. Everypony does except Destroyah. Rodan passes overhead and triggers a massive sonic boom and blast of hot air. Soon, flames cover his body until he resembles a phoenix, then he loops around.
At the same time, Rainbow Dash flies to Foal Mountain and then loops around. Pushing herself to her absolute limits, she unleashes what is possibly the biggest Sonic Rainboom of her life.
Cloudchaser does her best to steer the weather factory away from the Cloud Gremlins' dark cloud and lightning strikes, who gloat that it's only a matter of time before they catch up. Suddenly, Rodan and Rainbow Dash smash into the dark cloud at the same time from opposite sides, obliterating it
. A massive explosion of fire and rainbows results, and the resulting shockwaves cause heavy damage to the weather factory. Rodan and Rainbow fall out of the sky in an arc.
The two are sent sailing all the way back to Ponyville, smash through the finish line, and land in a pond. Throughout the whole experience, Destroyah didn't budge an inch and was completely unfazed by the shockwaves and heat, to the point Scootaloo was able to use her body as a shield. Everypony checks on the now steaming pond and Rainbow and Rodan emerge from it battered and bruised. The two burst out laughing from their awesome experience. She again offers him a hi-hoof and this time he returns it. Rainbow says they will definitely do great in the airshow.
Meanwhile, Monster X and Aria Blaze spar with each other in a snowy field. Throughout the 'fight' the former is lecturing the latter on her technique on issues like keeping her move set diverse, not throwing her shoulder, and keeping a good stance. Adagio Dazzle and Sonata Dusk left to try to feed on nearby humans' emotions. X eventually bests Aria and knocks her down. She complains that she wanted him to teach her about her new powers, not hand to hand combat. In her anger, the gravity around her briefly distorts. He lectures her that gravity control is a full contact ability; it requires your entire body to perform, so practicing martial arts is essential to use it. Additionally, since he had become aware she came from a form very different from a human, this was a good way for him to make sure she knew how to control the human form properly. Aria however gets annoyed, but takes comfort that her new abilities make fighting easier. His blows don't hurt as much and her blows are a lot stronger than before.
He comments that her long hair is a liability and tells her to get a haircut, but she yanks on his scarf and calls him a hypocrite for literally wearing a cord around his neck. Annoyed, he backs away and says it's his turn for training to get his own power under control. Monster X begins to power up. He muses in his head that this snowy field will prevent the pitch black Enjin from sneaking up on them, plus snow is great for practicing gravity manipulation. He concentrates and slowly begins to levitate a short distance off the ground.
Next, X gathers energy and forms them into balls of condensed plasma. Even though they are barely the size of water droplets, the concentration and strain he requires is enormous, and he's soon in pain. Suddenly, his mind is filled with anger, hatred, and anguish and Kaizer Ghidorah attempts to take control. Aria sees his white hair slowly turn black and gold. Alarmed, she sings the song she sang the night Kaizer attacked her in the tree. X feels the negative feelings leave him and he is able to calm down and dissipate the plasma balls. X starts releasing red smoke that Aria quickly absorbs.
X focuses and causes all the falling snow in a two meter radius around him to stop in mid air. Then he gathers all that snow into an ice ball. Calmed back down, X drops it to the ground and stares at Aria. After absorbing the red smoke, her hair and skin is darker and her eyes have turned red again. He asks what she did, and she snarks that she stopped him from flipping out, as she likes not having her neck broken.
