Cosmoem pulsed, and they were on a giant altar in the middle of a canyon.

"There!" the Psychic-type said, then wobbled a bit. "That was a lot of people to teleport at once…"

Ash reached out to hold them up. "Wow, you're a lot lighter than Zoroark is when he turns into a Cosmoem."

"I'm pretending to be lighter, don't tell anyone," Cosmoem whispered.

"Hey, Ash," Pikachu said, getting his attention. "Is it me or is this exactly like that place we dreamed about?"

"Oh, yeah, it is!" Ash agreed. "Where is this place, exactly?"

"This is the Altar of the Sunne," Burnet answered. "Lusamine, Faba and I were here only a week or so ago to track some Ultra Aura signatures… maybe that was related to the dream you mentioned?"

"Oh, come on!" Tapu Fini said from atop one of the spires, drawing their attention. "You're early! Hold on a minute, I need to get the others."

She vanished.

"Early, huh?" Ash asked. "Well, I guess we should look around while we wait for Tapu Koko, Tapu Bulu and Tapu Lele to show up."

"You're-" Burnet began, then stopped. "I was going to accuse you of taking this far too calmly, but then I remembered that the creator is literally your phone and I have to admit that I would have no idea how to handle that situation. Let alone the rest of your… you."

"Well, Arceus One isn't my phone, my phone is Arc, a shiny copy of Arceus," Ash corrected. "Arceus One was actually really surprised that Mew managed that!"

He looked down at Cosmoem. "Let's have a look around! Oh, wait, if this is the Altar of the Sunne, is there an Altar of the Moone too?"

"There's stories about it, but nothing confirmed," Gladion provided.

Ash nodded. "Right… well, let's see what the Altar looks like, right, Cosmoem?"

Ten minutes later, everyone was sat around the upper level of the altar and Ash was taking some star bit sweets out of a bag.

"You liked these, right?" he asked.

"Yep!" Cosmoem agreed, and pulsed happily as Ash gave them one. "They're stellar! Is that a joke? I tried my best with it!"

"It sure was," Ash confirmed. "Well done!"

Then Tapu Fini came floating back, along with the other three Guardians.

"See?" Tapu Fini asked. "I told you they were early."

"Fine, fine already," Tapu Bulu complained. "I listened, didn't I?"

"I don't know why you thought he was predictable in the first place," Tapu Lele said, as Tapu Koko landed and sprinted ahead to inspect Ash.

Then he nodded. "Just as I thought!"

"Just as you thought?" Fini asked. "Did you have some kind of warning about this?"

"No!" Koko replied. "I just sort of guessed. Anyway, let's get on with this!"

"We probably should," Fini conceded. "Cosmoem, are you ready?"

"I'm ready," Cosmoem agreed.

"Ash, you are the one who was assigned to take care of Cosmoem," Lele announced. "Are they ready?"

"Could you, for example, now throw them through a window?" Koko asked.

Bulu gave him a look. "What kind of question is that?"

"Mostly personal curiosity," Koko replied.

"Cosmoem says they're ready, and I believe them," Ash answered. "And I'll be there to help them out!"

"Well said," Lele decided. "Place Cosmoem on the focal point of the altar."

Ash did so, and Cosmoem pulsed. The stone of the altar changed, the slight imperfections from sun and wind vanishing, and all four Guardian Deities began humming.

Their Terrain moves mixed into a single combined whole, and the ground began to glow.

"Child of the stars," the Tapus chorused. "Pass into your inheritance."

Cosmoem flared with light, then with a massive flash of silver energy turned into Lunala.

The humming stopped.

"Um," Koko said. "Was that supposed to happen?"

"I'm pretty sure this is the Altar of the Sunne," Lele frowned. "Fini? We didn't get lost, did we?"

"Hmm," Lunala said, then furled her wings. The whole of her silvery form collapsed back into her starry face plate, which reverted to Cosmoem, then Cosmoem lit up with a golden light and instead evolved into a Solgaleo.

"I was thinking!" Solgaleo said, landing with a four-pawed thump. "About what it takes to evolve Pokémon, and I decided to do science. Science means doing experiments! So I teleported the base plate of the Altar of the Moone to swap it with the one from the Altar of the Sunne."

He sat on his haunches, looking very smug. "And it turns out that just the base plate and the ritual is enough to enable me evolving into a Lunala, and just the rest and the ritual is enough to enable me evolving into a Solgaleo! So I chose both!"

"That's great!" Ash said. "Well done, that's a really useful experiment!"

"...do you think his parents planned this all along?" Fini asked Bulu quietly.

"I mean, who knows, but it is a bit of a trend apparently," Bulu replied.

After changing back and forth a few times, Lunala decided that it might make things simpler if she had a nickname just so that everyone could tell her apart from her parents.

"I know my name's different to Solgaleo and Lunala's, but it'd be easier for humans if there was a way to talk about me, right?" she asked. "And I have human friends!"

"What about Nebby?" Lillie suggested. "For Nebula… it's sort of like Snowy's name."

"Oh, that could work!" Lunala agreed. "I'll think about it and probably say yes! Now, um… how do I open an Ultra Wormhole to somewhere specific?"

"You'll need help, at first," Tapu Fini said. "Koko, I know we were going to help evolve Cosmoem into Solgaleo specifically, but did you-"

"Of course I brought both Z-crystals!" Koko replied, rummaging in his armour and bringing them out.

"Good," Fini decided. "Now… Ash, in order to allow you to-"

"Already did it," Koko interrupted. "That's how Ash and Pikachu nearly blew me up with the custom Electric crystal. Why would I not give them a Z-power ring?"

"You really don't know what restraint is, do you?" Bulu asked.

"Umm…" Koko said, seeming to actually consider it. "I've heard of it, but I don't think I can come up with an example."

"How are you not-" Lele began, then stopped. "Okay, I'm going to try to forget I ever had that idea in case you hear it."

"In order to allow you to help Lunala, or Solgaleo, to form an Ultra Wormhole," Fini tried again. "You will have to help them perform their special Z-move. For Solgaleo it is called Searing Sunraze Smash and for Lunala it is called Menacing Moonraze Maelstrom."

"Oh, I get it!" Ash said. "Steel and Ghost type… well, I know the Ghost moves already so that's the one we should start with, okay?"

"Right!" Lunala agreed. "Also, I decided, I'm Nebby now."

"Everyone, form up!" King Dragonite decreed. "Whoever's going through the wormhole should be able to fly at high speed, and anyone who isn't should either ride or return themselves."

"Can you fly, Silvally?" Gladion asked.

"Eject R," Silvally replied. "Let's find out."

Gladion realized what Silvally meant, and took out the Flying-typed Memory from the case – swapping it with the Dark one.

Then Silvally rose slightly into the air.

"Apparently the answer is yes," he said. "I would be honoured to have you with me, Gladion."

Ash and Nebby struck their poses together, then Nebby blew a hole in the universe with her Z-move.

"Wow," she said. "That was easier than I was expecting, to be honest. It's sort of like teleporting but you wedge it open in the middle."

"Let's go!" Ash called, swinging up onto Latios' back. "It's time to rescue Director Lusamine!"

Latias went swooping through first, without a passenger, and Latios tilted to the side a bit as he listened to his sister.

"Apparently it's not all that turbulent," he reported. "It's weird on the other side though."

Noivern began humming a catchy song about going through a wormhole, and one by one he, several Dragonite, Nebby and Latios all went zipping through.

The inside of the portal was glowing and pulsing with energy, starting to visibly close off behind Nebby as she flew through, and Latios twitched his wings a bit before accelerating to overtake Nebby and get out of the Ultra Wormhole in front of her.

"Thanks, Latios!" Ash told him, sliding back onto the ground, then helped Zygarde out of his bag. "I think you'll have to go through last in future, Nebby."

"Got it, Ash!" the Lunala agreed.

She looked back at where the Ultra Wormhole had been, then switched to Solgaleo and had a look around. "Wow. This place is weird."

"It's like we're at the bottom of the ocean, but there's air," Lana frowned. "Wait – there's lots of those Ultra Beasts around!"

"Burnet said they were codenamed UB-01, Symbiote," Gladion said. "But these ones aren't attacking… you might be right, Ash, we only see the aggressive ones in our world."

"It's a pity we can't talk to them," Kiawe frowned. "Wait, can we? The one that kidnapped Lusamine, when it said something I just heard gibberish."

"Yeah, their accent was really weird," Ash agreed. "I didn't get it."

Lokoko jumped out of her Pokéball. "I didn't understand it and couldn't translate," she admitted. "I feel like it's not really very polite of them, somehow, but that's unfair of me."

"I am working on the problem," Arc advised.

"Wait – look!" Lillie pointed. "There!"

One of the Symbiote Ultra Beasts floating in the middle distance had a human contained inside it, with her head and torso inside the main bubble-like body of the Ultra Beast and her legs hanging down outside.

"I think that's mother," Gladion agreed. "Her hair's changed colour, but… it's her."

"Go away!" Lusamine said. "They're mine!"

"Woof," Zygarde announced. "Attempting pawshake."

They frowned. "Hmm. I appear to have forgotten to bring sufficient Cells here into an entirely different universe. Aura Break is not available."

Then suddenly Lusamine vanished from inside the Symbiote, and tumbled out from just behind Lillie.

"Spectral Thief," Marshadow added, helpfully.

"Mother," Gladion said, crouching down to pick her up. "It – how did that work?"

"I stole her," Marshadow explained. "It's actually quite a simple process."

"Give her back!" the Symbiote demanded. "I took her, she's mine now!"

"Oh, huh, we can understand you now!" Ash said. "That's neat! Hey, would you mind explaining how to translate your language?"

The only answer he got was a hissing sound, then the Symbiote used Venoshock and spewed out a whole lake of poison.

Nebby crouched down so as many humans and Pokémon as possible could get on his back, Gladion swapped out Silvally's Flying Memory for a Steel one, and Ash grabbed Zygarde to get them both into the air on Latios again before the hissing poison arrived.

"I guess we're going to have to fight," Ash decided, double-checking that all his Dragons were airborne. "Salazzle, don't set it off but it'd be nice to have some Pecha mist!"

"On it, boss," Salazzle confirmed, sending himself out and exhaling.

"Rock and Poison type," Lusamine murmured, from Silvally's back. "I… think that's the right type. It was so hard to think, but…"

"Requesting permission to handle this," Zygarde stated.

"Sure!" Ash agreed.

The dragon-dog jumped from Latios to Latias, and cleared their throat. "Ahem. Thousand Arrows."

Once Thousand Arrows had taken place, and with the Symbiote flattened into the floor, Silvally paced over through the Venoshock to look closely.

"That is the same one that attacked before, that I protected Lillie from," he said. "I recognize them."

"And none of the other Symbiotes… we should really learn their real name… none of the other ones are coming over to help this one," Ash pointed out. "I guess that means it's only really this one who's trouble… and they know that we can come and sort things out if there's trouble again! So we should head back home, now. Does anyone know the Steel-type Z-move poses?"

"Sorry, but is nobody else going to comment on this?" Lusamine's Salazzle said, pointing at Ash's. "He's a Salazzle! That is not a sentence I expected to ever say!"

Ash's Salazzle shrugged. "Eh, it is what it is."

Burnet looked up as an Ultra Wormhole opened, then started counting under her breath as a procession of dragons came through. Then Silvally, with her boss on his back along with her children – then Nebby, who came through last and closed the Ultra Wormhole behind him.

"That was impressively quick," she said. "You were only gone about fifteen minutes."

"I insisted we stay long enough for Ash's phone to take some readings," Lusamine said, then practically fell off Silvally as the Synthetic Pokémon touched down.

"Sorry," she added. "It's… been a day."

"So, what happens now?" Burnet added. "We definitely know where Ultra Wormholes come from, or some of them at least, and we know that Nebby can create Ultra Wormholes… what does that do to our direction of study?"

"I'll have to think about it," Lusamine said. "After I've had time to think, anyway."

She rested her hand on Silvally's neck. "And I think we really need to have that talk with Doctor Faba about what he's been doing without my approval…"

Arc went bing.

"I am finished," they said. "I considered several possibilities for how to fulfil the objective of: talk to Ultra Beasts, and I have decided on the ideal approach. Please check the home screen."

Ash did so.

"Oh, huh, a new app," he said, tapping it. "There's something about a learning curve?"

"Correct," Arc agreed. "This new language app will work to add translation based on known information. There is also a digital Hoothoot which provides helpful facts."

"A Hoothoot?" Ash's Rowlet asked, peeking out of Ash's bag. "Why not a Rowlet?"

"I decided it would avoid confusion," Arc explained.

"Oh, fair enough," Rowlet decided. "It might be confusing to have two Rowlets. Hi Solgaleo! Where did Cosmog go?"

"That's actually me," Solgaleo provided. "I evolved. Twice."

"Congratulations!" Rowlet said, perching in Solgaleo's mane, and evolved to Dartrix.

"Does that work on all Rowlet, or just yours?" Sophocles wondered. "They do charge up in sunlight…"

Ash was still looking at Arc's screen. "Oh, huh, so the Symbiotes are actually called Nihilego! That is a helpful fact, great work Arc!"

AN:

This seemed like the obvious solution.

I'm not sure why in retrospect, but...