Ash, Ash-Greninja, Pikachu and Zygarde got to Lumiose Gym first, with Greninja forming a trio of bubble clones before flinging Ash and Zygarde up the side of the tower.

Thanks to ninja fast-movement, there were already other Greninja clones up there to catch them, and Ash gave his Water-type a thumbs-up.

"Thanks, Greninja!" he said. "Now, let's rescue that Zygarde!"

"Right!" Greninja agreed, pulling a water shuriken off his back, and threw it at the nearest doors. They opened with a whoosh, sending the shuriken straight through, and Greninja winced as the shuriken smashed into a wall and ruined the paint job.

"...oops," he added. "I forgot, this place is full of automation."

He looked at the sensor over the door. "It's sort of impressive they open that quickly though."

Once inside, it only took two corridors to reach where Zygarde was detecting the pulsing interference signal, and as they entered the room Zygarde pulsed and generated a tesselated-hexagon shield around itself.

"Aura Break engaged," they stated. "The interference is being kept from influencing me."

"Great," Ash said. "Can you save the other Zygarde?"

"Unclear," Zygarde replied, antenna raising.

"Where did you get a Zygarde – is that a Zygarde?" one of the people in the room asked, then shrugged. "Well, it won't do you any good."

"Who are you guys?" Ash said. "You must be Team Flare, right?"

"Of course," the man agreed. "Allow me to introduce us. I am Xerosic, the leader of Team Flare's Science Division."

He indicated the four others behind him. "These are Aliana, Mable, Byrony, and Celosia."

"How did you know we were Team Flare?" Byrony asked. "I think we changed outfits since last time we were in public, you know, before the plan."

"Wait, hold on, that is Ash Ketchum, right?" Celosia checked. "Because, shouldn't he be on our side? We're doing this to help people like him."

"That's a good point," Byrony admitted. "Hey, have you heard our plans?"

"Yeah, and I don't agree at all!" Ash insisted. "Let Zygarde and any other Pokémon you've imprisoned go, or we'll have to save them!"

Greninja made a threatening hand signal, and Xerosic raised a hand.

"I think you'll find it quite hard to stop us," he said. "You may have powerful Pokémon, but there's nothing as powerful as Zygarde empowered by both Xerneas and Yveltal."

Pikachu's cheeks sparked. "I don't know, I think I'd be willing to test that. Hey, Zygarde, just to confirm, you're Ground and Dragon, right?"

"Correct," Zygarde stated.

"Good, I like a challenge," Pikachu said.

"So you've really got a Xerneas and a Yveltal prisoner to make Zygarde stronger?" Ash checked.

"...I don't like this, boss," Mable said. "He used the singular for both of them."

"It doesn't matter," Xerosic replied. "Yes, he does have that other Yveltal we've heard of, for… some reason… but that's why we used them both!"

"Connecting," Arc announced.

"Connecting to what?" Xerosic demanded. "Who said that?"

A Dusk Ball appeared in Ash's hand, then Shiny Yveltal came out. A moment later, a golden ring appeared in mid-air, and Gold came out.

"Greetings," said Clembot, from the corner. "Aren't you technically one of my siblings, as a fellow creation of Clemont?"

"I don't want to work out my family tree, it would be too confusing," they said, making a sort of portrait shape with their hands, then threw a golden ring.

Shiny Xerneas dropped through, wearing a VR headset with most of the support gear wrapped up in his antlers.

"Is something wrong?" he asked, taking the headset off with a hoof while balancing on the other three. "Professor Oak wanted me to test – wait, who are all those guys?"

He looked around. "Is it daytime? When did that happen?"

"Hey," Shiny Yveltal said. "So, quick summary from the text Arc sent. We need to help Zygarde to match another Zygarde in power."

"Oh, huh," Xerneas decided, nodding. "I don't know how to do that but I'm willing to learn!"

"Do Legendary Pokémon just drop out of the sky around you or something?" Celosia asked. "How did you even do that?"

"Well… that doesn't matter," Xerosic declared, as Zygarde began explaining what they knew of the procedure. "XYZ counters XYZ, but we've also got lots of Pokémon that can Mega Evolve!"

Arc beeped. "Connecting again."

"That must be a connection to the internet or something, but how's that even working?" Xerosic asked. "There's so much electromagnetic interference in here from Zygarde's Aura Break that even the land lines are suffering from problems. That's why we had to haul the robots in here!"

"And Behold, for the number of bars of signal strength shalt be four," Arc said. "And the gees shall be six."

"Is 6 G even a thing?" Pikachu asked.

"It is if I say it is," Arc replied.

Ash's Mega-Evolvable and Bond-Phenomenon-capable Pokémon arrived, which took up quite a lot of the room.

So did Zacian, who sort of counted.

"We don't seem to be in the Pokémon League," she said, deciding to act as spokesmon. "What's going on, exactly?"

"A group of idiots weaponizing Legendary Pokémon to do something or other, probably involving a superweapon," Pikachu summarized. "Hey, Ash, are you going to get ready to Mega Evolve too?"

"I should probably do that, yeah," Ash agreed. "But I don't think they're idiots, Pikachu, because doing all this must have been really hard and meant doing a lot of research. I just think they're really, really wrong."

"Did your Pikachu call us all idiots?" Aliana said. "I mean, wow. Rude?"

"Enough of this!" Xerosic insisted. "Ash Ketchum… you must realize that we've prepared for this situation as well?"

"I don't think we did?" Mable asked.

"All right, we didn't prepare specifically for there being a shiny Xerneas just… spare… out there," Xerosic amended. "But we did prepare for battling lots of powerful trainers, because we knew it could happen before we'd fully activated the superweapon."

He coughed. "Admittedly part of the plan was to recruit Ash, but that's not the only thing we have ready to go!"

Mirage Mew went bing.

"Oh!" they said. "There's something up in Lumiose! I'll have to head over there right now!"

"Huh?" Saturn asked.

"Do not worry, another instance will handle it," the virtual Pokémon said.

At about the same time, right at the top of the tallest tower in Mirage Mew's lunar landholding, a Mirage Generator flickered to full power.

It generated another Mirage Generator, already spun up to full power, about a hundred metres in the air. That new pseudogenerator made another one in turn, another hundred metres into the air, and the first mirage Mirage Generator dissolved again as the second one generated a third.

Mirage Mew had many ways to get from the moon to the Earth, but sometimes it was nice to take the scenic route.

"We've built our superweapon to resonate with the structure of Lumiose Tower," Xerosic warned. "It's contained for now, but the moment that the structure takes significant damage it'll activate ahead of time… and I don't think you want that, right?"

"Then we'll just have to get help to add things to the tower!" Ash said. "Arc, can you get my Nephmew?"

"How could you…" Xerosic began, then stopped himself. "What do you mean, add things to the tower?"

"Well, if it's resonating, and taking things away activates it, then adding things will screw up the resonance!" Ash said.

Mirage Mew appeared. "Hi! Sorry for the delay."

"Great to see you!" Ash told the virtual Mew. "You're really good at fast building work, right? Can you add some extra bits to the tower without making the resonance inside it get out of control?"

"I can!" Mirage Mew confirmed, and vanished again.

"…sometimes it's very hard to be a science expert," Xerosic grumbled, then shook his head. "But that's not all I've got set up! We've got…"

He stopped, and turned to whisper to Aliana.

Ash waited, because it was polite.

"Really?" Xerosic asked. "Huh, well, it should still work…"

He turned to Ash. "We've also got a Giant Rock!"

"A giant rock," Zororark repeated. "A giant rock? Is that really what you're down to?"

"It's not just an ordinary giant rock," Byrony said, stung. "It's a Giant Rock charged up with Primal Energy!"

She hit a control, and something outside made a groaning, grumbling sound.

Ash hurried over to the window to see, and spotted it almost straight away – a giant, glowing rock, on the pavement outside next to the large truck that had apparently carried it there.

It helped that Rayquaza was hovering next to the rock with a knife and fork.

Then the groaning, grumbling sound came again, and Rayquaza startled backwards before looking around and flying up to Ash.

"Is something wrong with it?" she asked. "The first bit was really really tasty, but there's a lot of it and then it started growling… did I do something wrong?"

"I don't know?" Ash replied. "It's something to do with that rock being full of primal energy, I think."

"Full power," Xerosic decided, turning a control dial, and the rock began to glow in an eerie sort of way. Then it changed shape and size, forming into a massive animated-rock version of Zygarde's serpentine fifty-percent form.

"Searching records," Arc announced. "Solution found."

"What?" Celosia asked. "What do you mean, solution found? How can you possibly have found a solution to that?"

"Connecting," Arc said.

Then Ho-Oh tumbled out of his materializing Pokéball.

"I'm awake!" he announced, then looked down at the ground.

"Zygarde, what happened to you?" he asked. "Don't worry, I can help!"

A few minutes later, the very brief period of fighting was over and Ash was back at street level.

"How do you feel now?" he asked the big shiny Zygarde looming overhead.

"Alive, which is new," the big shiny Zygarde replied, inspecting its turquoise forepaw and then the white one. "I am not clear on whether I am made out of cells or not. It is quite confusing."

"I agree," said the familiar Zygarde who'd been travelling with Ash since Johto. "This is not within expected parameters. It is, however, better."

They looked up at the Big White Dog. "Do you have a plan about what to do now?"

"I do not," Shiny Zygarde admitted. "I have not been in a situation to plan for the future before. I would appreciate assistance."

"I have a suggestion," Mirage Mew said. "What is your opinion on spending long periods of time in the same place, thinking?"

"It would be quite pleasant," Shiny Zygarde decided, after considerable thought. "It would be useful for me to understand better how to be a Zygarde, though. I do not know if Zygarde are meant to be singular or plural."

Specimen Z, the Zygarde Core that Team Flare had been using (which had accepted the designation Z2 to reduce confusion) raised a paw.

"I have an idea," they stated. "This core will accompany Shiny Zygarde in teaching lessons about how to be a Zygarde. The other core will continue to accompany Ash until the decision is made not to."

"That sounds good," Shiny Zygarde decided. "What is your suggestion, virtual Mew?"

"Well, one thing that really improves public spaces in my experience is statues," Mew replied. "You could take up a career as a statue."

Over where Team Flare had been captured, mostly by Ash's Pokémon except for Lysandre (who'd been captured by Alain), Mable raised her hand.

"What just happened?" she asked.

Lysandre considered.

"I can explain, if you want," he said. "How many hours do we have?"

AN:

It's always nice to get help from friends.