@Ultimate CCC

I imagined Pikachu's Charge Beam coming out of his forehead, but now that I actually think about it, that makes no sense, so maybe we treat it more like a Hadouken from Street Fighter or a Kamehameha from Dragon Ball?

Anyways, ONTO THE STORY

"Face it ever since we went separate ways from Cheren and Bianca we are hopelessly lost." Rosa complained.

"Look, I'm sure we'll find a way out of here in no time." Ash responded.

'Chick chick chick'

"Hey guys, do you hear that?" Elliot asked.

"I wonder what is making that noise?" Ash asked, trying to find the source.

"Are we just going to forget finding our way out of here?" Rosa questioned.

"Yeah, don't worry, plus there's a chance whatever is making that noise knows the way out." Ash said, looking around a corner. "It's louder in this direction, come on!"

"That's not normally what people run too!" Rosa said, chasing after Ash and Elliot.

A few twists and turns later

"Whoah, this is…". Ash said unable to come up with a way to describe the giant nest in front of them,

"A lot of Durant." Elliot commented, seeing the bug types.

"Durant?" Ash asked.

"Bug and Steel types, it's strange usually they're more under control than this." Elliot commented.

"Can you say that in simpler terms?" Ash questioned.

"Seriously, you don't have Durant problems in Kanto?" Rosa asked. "They're a pest, and usually something like this is controlled by a couple of Heatmor."

"Let me guess, fire types?" Ash asked, the two nodding. "I mean it's not like they're harming anything here."

"No but if left unchecked it could become a much larger problem, even creating weak points in the mountain." Elliot informed.

"Well if fire is all we need, then come on out Larvesta!" Ash exclaimed, sending out his bug type.

"Vest." Larvesta said, prepping himself.

"Use Ember!" Ash called out.

"No don't not like this!" Rosa called out, as a flurry of embers shot at the nest, dealing minimal damage, before dozens of red eyes began glowing from inside the nest.

"I'm guessing there's more to Heatmor than just it being a fire type for this." Ash commented.

"Yep." Elliot said.

"Okay then, on my mark, RUN!" Ash exclaimed, scooping up Larvesta and PIkachu as he chased after the already fleeing Rosa and Elliot.

A few minutes of running and hiding later

"Okay, two things, one definitely not trying that again, and two there's no way I'm leaving here with that kind of mess still present." Ash said, catching his breath. "You said Heatmor usually handles this, any chance of there being any here?"

"From what I recall, not even Larvesta are normally found here." Elliot remarked.

"Meaning it's an invasive species right now." Ash realized. "Okay, option two, do either of you know what makes Heatmor so special about dealing with these?" Ash asked.

"They're probably stronger than Larvesta." Rosa mentioned.

"Unfortunately Larvesta isn't great when it comes to ranged attacks." Elliot said. "Maybe we should just head for Undella Town and tell someone when we get there."

"I guess you're right. Alright Larvesta, return." Ash said, now noticing his bug type was no longer in his arms.

"Where's Larvesta?" Rosa asked.

"One good guess as to where he is, and I'm not happy about it." Ash groaned, walking back towards where the Durant were.

Ash slowly made his way back to the Durant den to notice a stream of hot silk coming towards the nest.

"Wait, Larvesta?" Ash asked, noticing the bug type in a lava pool.

"Larvesta are known to make their nests in volcanoes. So I guess he's naturally just used to being in lava." Elliot admitted.

"And look at his silk, it's attacking the nest." Rosa said.

"Larvesta, this is impressive." Ash said in shock.

"Veeeeeeeest." Larvesta said, finally finishing shooting his silk.

"RANT!" A single large Durant exclaimed, scuttling out of the nest.

"Vesta!" Larvesta exclaimed back.

"Alright Larvesta, I trust you for this. Use Ember!"

Larvesta's horns sent out a flurry of flames at Durant, engulfing the larger Pokemon in flames.

"Rant!" The Durant exclaimed, scuttling forward at Larvesta, the two bugs colliding.

"What was that?" Rosa asked.

"I think it was Iron Head." Elliot commented.

"I think she meant Larvesta, and I think that was Take Down." Ash commented.

"But that's not good against a steel type like Durant." Rosa reminded.

"I know, but I didn't exactly give him a command." Ash reminded. "Larvesta use another String Shot!"

Larvesta sent out a shot of red hot silk, wrapping up the area the Durant were in.

"And now we get out of here." Ash said, returning Larvesta to his Pokeball.

"Why, Larvesta was holding his own." Rosa pointed out.

"Ant!"

"Ant!"

"Ant!"

A group of Durant launched at Larvesta's cooling silk, chomping away at it.

"Never mind, we run." Rosa exclaimed.

"To Undella Town, and hopefully before we run into something even worse!" Elliot exclaimed, keeping up with Ash and Rosa.

Ash's Current Team and their Moves

Pikachu: Quick Attack - Thunderbolt - Iron Tail - Charge Beam

Riolu: Aura Sphere - Blaze Kick

Servine: Wrap - Leaf Tornado - Energy Ball - Aqua Tail

Braviary: Super Power - Crush Claw - Hone Claws - Aerial Ace

Darmanitan: Hammer Arm - Flare Blitz - Belly Drum - Rollout

Trubbish: Sludge Bomb - Double Slap - Toxic Spikes - Sludge Wave

Larvesta: String Shot - Ember - Leech Life - Take Down

Dewott: Razor Shell - Fury Cutter - Revenge - Aqua Jet

Solosis: Telekinesis - Future Sight - Psychic - Rain Dance