It took Ash a long while to pick which of his Pokémon to use for the Grand Trial, especially since it was going to be one against three, but a combination of timing and wanting to test something out led him to pick Lycanroc.
"Good luck, okay?" Ash asked, giving the Dusk Lycanroc a scratch under the chin. "Let's do this!"
"You got it!" Lycanroc agreed, with a flick of their tail, then turned to face Nanu's first Pokémon.
Which turned out to be a Krookodile.
"Begin, or whatever," Nanu called. "Mud Slap."
"Stealth Rock!" Ash instructed. "Dodge into the air – then use Rock Polish!"
"Into the air?" Nanu asked, then watched with some disquiet as Lycanroc jumped over the mud-slap and didn't come down again. "Okay, huh. That's weird."
"Just a bit," Krookodile agreed.
Lycanroc was accelerating already, their Stealth Rock lifting up rocks for them to kick off of, then Ash pointed. "Okay, now use Rock Throw!"
"Counter," Nanu instructed, and Krookodile blocked with a straight-arm block, grunted, then threw the rock right back at Lycanroc.
"Okay, huh…" Ash frowned, thinking hard. "Counter is going to be tricky… use your Stealth Rocks to shield against the counterattacks!"
"Got it!" Lycanroc replied, bouncing from rock to rock, and randomly kicking some of them down at Krookodile using Rock Throw. The second Counter missed, then the third slammed into a shield of rocks, but the fourth one did make it through and hit.
"Whoops," the Rock-type muttered. "Hey, what about this?"
Lycanroc jumped from one rock to another until there were six of them faintly glowing at once, then launched them all down at once. Krookodile blocked, managing to catch one and Counter with it, but the other five knocked him onto his back.
"Back up," Nanu instructed. "Sand Tomb."
"Look out!" Ash called.
Lycanroc was already dealing with Sand Tomb, and it surged in to trap them in place. Then it trembled, and Lycanroc burst out of the sand again with Accelerock.
"What is it with my fur getting messed up?!" they howled, eyes glowing red, and kicked off three rocks before arriving right in front of Krookodile. Ash's Rock-type grabbed Krookodile by the tail, then took off again to drag Krookodile into the air, and Ash watched with care.
"Huh," he said, softly. "Pikachu, is it me or…?"
"I think you're right," Pikachu agreed.
Ash got the Rock Z-crystal out of his pocket, turning it over for a moment, then plugged it into his Z-ring.
The two combatants were almost too high to see for several seconds, then Krookodile came crashing back down and made a crater in the ground with a wham.
Lycanroc followed, eyes going from red back to green, and touched down gently. "I think I'm all right now," they said, shaking themselves, and the sand went dusting away in all directions.
"Careful, Lycanroc," Ash advised. "You did great there, but there's two Pokémon to go. Or, uh, still all three? I'm not sure."
"Yeah, two," Nanu said, returning Krookodile. "Sableye, you next – Mean Look!"
"Dodge!" Ash called, realizing that a move like that had to have a reason.
"No, wolf!" Lycanroc corrected.
They dodged anyway, but Mean Look connected and outlined Lycanroc in a fizzing corona of dark energy that held them stuck in place.
"Now, Shadow Claw," Nanu ordered, prompting his Sableye to run forwards and start slashing.
Ash's thumb rubbed over the Z-crystal, then he raised his hands to his mouth instead.
"You can do this, Lycanroc!" Ash called. "Stay strong, don't let those Shadow Claw attacks get to you! Me-wwwew!"
Pikachu giggled.
"...what?" Nanu asked, completely confused. "Are you trying to imitate one of my Meowth?"
A Stealth Rock beaned Sableye in the face, knocking them away from Lycanroc, then the Rock-type gave a sort of convulsive all-over shudder and broke free from the Mean Look.
"Accelerock!" Ash said quickly, and Lycanroc whirled on one paw before darting after Sableye. "And I was speaking Poipole in Mew! That's because Lycanroc has been around when I was explaining how to speak that, because it's an alien language, but you couldn't get it from what I said and Sableye couldn't either. That meant I could order Lycanroc about what to do without you or Sableye realizing!"
Nanu shook his head.
"Kid, you're weird," he said. "Sableye, Shadow Ball!"
Sableye duly threw a Shadow Ball, then used Shadow Sneak as well to try and hide away from Lycanroc's latest barrage of stones.
One of the stones was Lycanroc, who believed in being paws-on.
"Okay, new plan, same as the old plan," Nanu muttered to himself. "Mean Look now!"
Lycanroc froze halfway through a pounce, went thump into the ground next to Sableye and bounced, then half-a-dozen Stealth Rocks pressed in around them and lifted them out of Shadow Claw range.
"Blinding One, but that's infuriating," Nanu grumbled. "Well, then, Shadow Ball!"
A barrage of shadowy orbs hammered into Lycanroc, the Rock-type not able to dodge them all just with Stealth Rock pressure steering, and twice there was a crackle as the Shadow Ball drained away Lycanroc's ability to endure the attacks pummelling them.
Then Ash pointed. "Now! Accelerock!"
Lycanroc pushed off from the rocks around them, revealing that the Mean Look had worn off already, and slammed into Sableye with a blistering-speed pounce.
Then used Bite, just for emphasis.
"Okay, two down," Nanu said, as Lycanroc panted. "One to go, and I think you'll have some trouble with this one."
He held up a Pokéball, and sent out an Alolan Persian.
A very big Alolan Persian.
"Oh, is that a Totem Pokémon?" Ash asked. "I've got one of those, I think he's from around here."
"So much for shock value," Nanu grumbled. "Okay, Persian – he's weak, use Dark Pulse!"
"Not a he!" Lycanroc replied, then ducked just under the Dark Pulse and began taking off again. The follow-up Power Gem that hit them on the rump spun them around, though, and after that Nanu called for a Shock Wave which hit the Rock-type hard as well.
"Lycanroc, get ready!" Ash called, and began posing. "We'll have to do this at maximum speed!"
The Z-crystal transformed with a flash into a Lycanium Z, and Lycanroc whirled in the air to face Persian.
"Ready to dodge," Nanu murmured.
"Mew!" Ash said firmly, finishing the pose, and a burst of light flashed around both him and Lycanroc. Persian darted to the side… then stopped, confused.
Because Lycanroc hadn't come smashing down to attack. Not in a Continental Crush, not in a Splintered Stormshards.
Instead, the clinging, corruptive energies from the Shadow Balls had gone completely, and the Z-crystal in Ash's ring was back to being a Rockium Z.
"Z-Rock Polish," Nanu realized. "Clever, but… Gunk Shot!"
Persian fired out a Gunk Shot, covering Lycanroc with gunk, and their eyes flashed into red.
They charged down to ground level, moving with blazing speed, and Persian darted out of the way just in time.
Now it was Nanu's turn to start posing, and Lycanroc's blazing red fury meant they were just attacking over and over again without stopping to consider what that could mean.
"Lycanroc, focus!" Ash called. "Look out!"
Lycanroc howled, sliding across the stony arena, then charged.
Persian used Black Hole Eclipse, aiming directly at Lycanroc.
And the Rock-type vanished just before the attack hit.
"...what?" Nanu asked, as the Black Hole Eclipse knocked out the rock formation Tapu Bulu was resting on and sent the Tapu falling to the ground in a cloud of annoyance. "Where did the Lycanroc go?"
"Oh, yeah, that!" Ash said. "So, you know how Lycanroc gets really mad when someone messes up their fur?"
He rubbed the back of his neck, looking between the panting Persian and Nanu. "Turns out, actually, they don't get mad enough to not listen to instructions! Also, they were going really fast there."
"Blep," Lycanroc said, from their position hovering directly above Nanu. "Oh, sorry, I meant Accelerock."
The Rock-type smashed into Persian, knocking them out.
"Funny thing," Lycanroc added. "Once I connected messed up fur to having a nice comb afterwards, it was much easier to deal with."
Ash gave Lycanroc a comb with the special rock-fur rated metal comb, along with brushing off their fur in general, then when Nanu made an annoyed sigh and started looking at his watch Ash decided it'd probably be polite to actually finish the part Nanu had to be here for.
"Sorry," he said. "I wanted to make sure Lycanroc knew they were appreciated."
"I guess that makes sense," Nanu admitted. "But I've got to ask, kid… why did you use Lycanroc? I mean specifically, he's a tough Pokémon but-"
"Still not a he," Lycanroc grumbled.
"Lycanroc's not male or female," Ash explained. "I get you didn't know that, it's fine, but now you do!"
"Right," Nanu said. "Anyway, uh, they're a tough Pokémon but I only said no legendaries and you knew it was going to be a tricky fight. Why not that Pikachu of yours?"
"You said no Legendaries," Ash pointed out.
"Does that technically count?" Pikachu asked.
Ash scratched him, and Pikachu made a sort of chirping purring noise. "When we were going around Sinnoh, a while ago now, there was this weird thing where we went to the past? And Pikachu blocked a direct attack from Arceus, so he ended up in legends as the Thunder Beast of Michina! It's really cool, but because he's in legends it feels like a grey area so I didn't want to use him without specifically asking."
Ash shrugged. "Besides, it was good for Lycanroc's development. It was them or Torracat, and she's still working on being able to do Battle Royales herself… I could have used Salazzle, but he didn't want to come here, and nor did Dartrix because he was too busy sunning himself."
"...he?" Nanu repeated. "Oh, whatever. Okay, kid, time for the Z-crystal…"
He rummaged around in a bag, then stopped, and looked up at Ash.
Lycanroc slowly rose into view over Ash's head, the canine Rock-type's head pillowed on their paws and their tongue out.
"...yeah, I don't think you should have the Dark-type one," Nanu decided.
"Actually Dark would be pretty good!" Ash said. "Or Fighting. Hey, Pikachu, want to see if you can do Z move poses?"
Nanu blinked. "What. Why would that. What."
He rubbed the bags under his eyes. "What are you even talking about?"
"Well, I know Secret Sword, Night Slash and Foul Play, so those would be good moves to try and Z-move, but I also know Razor Wind and Twister so it's not necessarily required," Ash shrugged. "Though I guess it'd be especially good to have a Fighting one because Pikachu can do that one too… do you have a Fighting one?"
"I might," Nanu said, deciding to just gloss over the whole I know thing, and also ignore how much Pikachu was now laughing.
It was a lot.
The moment that Nanu had confirmed Ash was safely off Ula'Ula – not that that meant anything – he practically ran for his office.
"You didn't warn me," he said, without preamble and as soon as his phone had connected. "Yes, I know what you said. I remember every conversation we had while you were hiding from a young boy here on Ula'Ula. I know what you said when I told you he'd arrived. You didn't warn me. His Pikachu blocked an attack from the creator god, how is that not something you think I should know?"
After more than a minute, most of which had just been listening to the sound of a bottle being opened and a glass being poured, Nanu blinked. "What do you mean, you don't know that? You know everything else! How would you not know this one just because it happened so long ago it's a legend?"
AN:
This marks the first time I've used a Z-status move. Which is one more time than the anime did it.
Unless you discount Extreme Evoboost, but then again Brock's Eevee did that once in this fic. So still applies.