Foreword:
As Ash feel asleep, he was taken into a dream, not one he usually has, but like the one he had when he met Arceus and all the other legendaries in the Hall of Origin. What do the Pokemon need now?
Ash woke up in the Hall of Origin, and he started walking to the place where all the legendary Pokemon gathered up before. Once he arrived there, he saw the Pokemon, but they looked, distressed? Arceus caught a glimpse of Ash. "Everyone, young Ash is here." Arceus called out. "Why did you bring me here, you all look worried about something." Ash said. They all looked surprised that Ash was able to catch on quickly. "Well, it is regarding you and another being, from another universe, maybe multiverse." Palkia said. Ash was confused. "What is a multiverse?" Ash asked. "A multiverse, we don't know exactly what it is yet, but we think it is a place where many universes are, like galaxies, but made of universes." Palkia said. "So this other being is from there, ok, and what do I have to do about it." Silence ensued the hall, until Arceus spoke up. "You know you have the power to manipulate Aura, right Ash? Well, it had only just recently awoken, but what is strange is that it merged with the other powers you have." "What do you mean by other powers?"
"What I mean by other powers is you being able to use the Bond Phenomenon, you being the being of willpower, and the chosen one." Arceus said. Ash knew where he was going with this. "So your saying, that all of those powers merged with my Aura, to create something else?" "Right on point Ash, once your newfound power has fully developed, you will be more powerful than me." Ash got shocked. "This is essential for the future of the Pokemon world, this being is coming to take over this world, it nearly did this once before." Arceus said. "The being struck a region called the Galar region, with an energy you humans call Dynamax energy, about 3000 years ago, when Galar and Kalos were fighting each other in a war. This energy made pokemon grow gigantic, with them having more powerful moves, and some even changing their form."
"However, what angered this being was the weapon that was used to end the war, the weapon constructed by AZ." Ash already knew about the story of AZ and The Ultimate Weapon. "This made the being go on a rampage, controlling all the Dynamaxed Pokemon to go on a rampage and destroy each region, for the being to take control of the Pokemon world. The being was eventually defeated by a hero, and two Pokemon I didn't create. You, are a descendant of the hero, and the two Pokemon that defeated the being were called Zacian and Zamazenta. The thing is, the being was only using a mere 1% of its power, why is because it was charging up its power for another takeover, this time on a multiverse scale." Arceus said. "Ok, so what do I have to do to stop it, and what should I refer, 'that being' to?" Arceus thought about it. "Call it Eternatus, I choose the name because it has been living longer than me." Ash was surprised to hear about a Pokemon older than Arceus. "That is all I know about Eternatus though, but one more thing, when Eternatus was defeated, it left behind a flower, which AZ's floette holds, the eternal flower. I find it strange that when you are in your battle bond with greninja, it matches the colour scheme of Eternatus and the Eternal Flower. You will find more out later, but that is all I can tell you for now." Arceus said. "Wait, that Riolu you have, we actually sent it to you, it has special Aura capabilities, and can help you train your Aura." Arceus finished. "Can I go back now, I will learn about this." With that done, Ash woke up.
"Riolu huh, what powers do you have..." Ash fell back asleep.
The next day, Ash woke up with a jolt. He checked the time. "Two hours before I usually wake up, may as well talk to Riolu about my powers." He took Riolu's Pokeball and walked towards the Beach. "Alright Riolu, I choose-" Before Ash even finished what he said, Riolu came out. "Ash, you kept me in that Pokeball for ages, why?!" Said Riolu, clearly frustrated. "Sorry bud, I couldn't let you be seen by anyone. Anyway I have something to talk to you about." Riolu listened. "You know I can use Aura right? Well my Aura powers have sort of merged with the other powers I had-" "I already know Ash, I knew ages ago, when I met you. Let me guess, Arceus told you I was sent to see you." Ash nodded in agreement. "Anyway, how do I use this power?"
Riolu got into a battle stance. "First, get into this battle stance, then just imagine you are trying to form some sort of attack, once you formed it, tell yourself how you want the attack to go, then let it loose." Riolu said as it used an attack much like Blast Burn. "Wait, you can use Blast Burn!?" "Only I can use Blast Burn, I have a strong Aura, remember that, you should be able to do that as well, you are more powerful than me after all. The colour of the attack depends on what type of Aura you have."
Ash then focused, he got into a battle stance, and then concentrated. He wanted to form a Blast Burn, like Riolu did. Flames then grew on Ash's arm, then he punched the ground, releasing a powerful Blast Burn, this Blast Burn was a rainbow colour. "A rainbow colour, does that mean I have a rainbow aura?" Ash asked Riolu. Riolu didn't respond. "Hello? Earth to Riolu?" Riolu was shook out of it's trance. "Your Aura is a strange one Ash, we will figure more out about it soon." Riolu said.
"Right, lets go have breakfast now, I am starving after that."
"Yeah, I am hungry too, lets go."