No one wanted Gray Moth's return to cause such a commotion every time, attracting all the surrounding Honkai Creatures and turning every homecoming operation into an event marked by great sacrifice and panic.
So, although the noise from the engine system tuning was loud enough to be heard throughout the base, everyone sensibly endured their annoyance.
But that was before. Now, all that tolerance vanished with the noise-canceling earplugs Yiselian handed over. Proper earplugs were definitely more effective than stuffing their ears with random bits of cloth.
Thinking of the days of noise assault, and then looking at the earplugs in his hand, Ryn put on a friendly face and wrapped his arm around Yiselian's neck.
"Earplugs are standard issue only for the Gray Moth troops… these extra ones were left behind by those who were sacrificed. So don't overthink it. It's not that we didn't want to give them out, we just really didn't have any extras."
Hearing Yiselian's words, Himeko walked over from the side.
"Enough talk. Let's begin the experiment. This place is very open, enough for us to test the engine."
This was a large, flat area, with very few buildings around. The advantage was not having to worry about being ambushed by Honkai Creatures from some hidden corner; the disadvantage was that the three of them would be sitting ducks once the engine started.
"I can already imagine the hordes of Honkai Creatures we're about to face."
Ryn shrugged and picked up a few rocks from the ground. These would be his ammunition for bombarding the Honkai Creatures later.
Himeko drew her Corona Greatsword and stood on Ryn's other side. Each of them was responsible for the Honkai Creatures on one side.
"What, scared before we've even started?"
"No, no, no, what I mean is… this is going to be a slaughter fest."
"Don't talk big and throw your back out. I won't be collecting your corpse for you."
"…"
Ryn looked at the rock in his hand, then tapped it against the back of his other hand. His hand was left without a mark, but the rock immediately shattered into pieces.
"Don't worry. According to my previous design schematics, the noise this time can be reduced to within 120 decibels," Yiselian said to Himeko and Ryn while tuning the engine system.
"Sigh, if only the nuclear reactor inside the Hyperion wasn't damaged, we wouldn't have this problem."
Himeko looked at the Hyperion's engine system with a nostalgic expression.
"I'm satisfied as long as it can still move. I don't have a problem with the noise. It saves us a lot of trouble by luring all the Honkai Creatures over to be eliminated at once."
"But it's not a good thing for everyone back at the base… It would be troublesome if we attract some strange enemies again like last time."
"Alright, enough idle chatter. Let's start the experiment."
Himeko put on her earplugs, ready for battle. Ryn and Yiselian followed suit, preparing to start the engine.
BOOM BOOM BOOM—
The moment the engine started, it produced a thunderous roar.
Immediately after, Honkai Creatures swarmed towards the engine like a plague of locusts, a black mass crushing everything in its path.
*This was a bad idea.* These damn earplugs barely blocked any noise. Ryn turned to look at Yiselian and Himeko, only to see that neither of them showed much of a reaction. It seemed they were used to it…
Amidst the engine's roar, the voices of people, or the sounds made by the Honkai Creatures, all seemed to fade into insignificance.
Himeko lifted her Corona Greatsword, unleashing fiery shockwaves one after another into the tide of Honkai Creatures drawn by the noise. A single slash of sword ki could kill a whole group, but an endless stream of Honkai Creatures would immediately fill the empty space, continuing their charge.
Ryn weighed the pebbles in his hand and threw them out like he was skipping stones. They created countless ripples in the river formed by the Honkai Creatures.
Normally, relying on the Authority of Gravity, Ryn could create an impact several times the speed of sound just by flicking the air.
Unfortunately, while this world looked like a material world, it was actually more like a spiritual one. The Authority's effects were on the material side, so its influence on this world was minimal.
Just like the powers of Creation and Withering, which were purely for manipulating matter, they had almost no effect in this "spiritual" world.
He wondered if the Herrscher of Sentience's Authority could wreak havoc here. But the Herrscher of Sentience's ability was to manipulate the "consciousness" of the material side; would it work on the "souls" of the metaphysical side?
As he was throwing, a thought suddenly occurred to Ryn. Bronya definitely didn't know about this engine test! Otherwise, she would never have sent just him and Himeko to guard it.
The engine ran for only a short time. Less than half a minute after it started, Yiselian shut it down and immediately began making adjustments.
But the number of Honkai Creatures drawn by the noise was not small. Although they weren't very bright, they would follow the crowd… The Honkai Creatures that arrived later had no idea what was happening, but they figured following the ones who had run over at the start couldn't be wrong.
Ryn and Himeko killed so quickly that the ones attracted by the initial noise were all dead, and the Honkai Creatures that followed behind without understanding the situation began to get confused. Most were already preparing to turn back and leave.
At that moment, Yiselian started the engine again. Hearing the noise, the hesitant Honkai Creatures that were about to leave immediately became energized again, roaring as they resumed their charge.
The old ones had fallen, and the new ones picked up the banner to continue the charge, while even newer ones joined their ranks.
This went on for a long time. Ryn had killed so many that he had dug a pit in the surrounding area and had run out of rocks to pick up. He eventually just started clearing the field with his Heat Vision, sweeping away a large area with each blast.
Himeko, who was in the middle of a killing spree, happened to glance over at Ryn's side, and her slashing motion faltered for a moment.
"Uh… we are supposed to be on a guarding mission, not an extermination mission, right?"
A moment later, the Honkai Creatures on Ryn's side were almost completely wiped out. Even when they heard the noise, only a few stray Honkai Creatures charged forward over the corpses of their kin.
But that only served to add a few more centimeters to the mountain of bodies. A single flying stone pierced through their heads in a chain, causing them to fall atop the corpse pile.
After finishing up on his side, Ryn turned to help Himeko.
Ryn flew in the air, continuously sweeping with his Heat Vision. Anyone he stared at died. Below, Himeko swung her sword, unleashing waves of scorching flames that wiped out large swaths of enemies.
Soon, the Honkai Creatures on Himeko's side were also nearly eliminated, with no subsequent reinforcements.
"Hey, you're not bad at all… I was originally planning to come back another day with Seele and Penglaiji Ryn to clean up another wave. Now, it'll probably be a long time before any Honkai Creatures gather in this area."
Himeko leaned on her Corona Greatsword to rest for a moment. A rare smile appeared on her usually cold face.
"You were planning to call Seele and the others… I'm getting the feeling this mission wasn't about protection at all, but more like a sting operation…"
Ryn looked speechlessly at Yiselian and Himeko. The engine system's noise hadn't decreased one bit; it was just as loud as before. On the contrary, the only achievement today seemed to be the complete annihilation of the surrounding Honkai Creatures.
"Don't say that… the engine's sound has been reduced a lot. It's already 2 decibels quieter than before, and the frequency isn't as piercing…"
Yiselian held up the new test data next to the old data in front of Ryn.
"Besides, the situation was different from before… It was mainly because you were killing them too fast that the Honkai Creatures kept charging over wave after wave. Normally, there wouldn't be so many Honkai Creatures. Most of them would retreat on their own after the noise stopped, and only a few that didn't leave would be eliminated…"
"Uh…"
Ryn shrugged helplessly. Who knew this would happen?
Then Ryn patted the engine system and said to Yiselian:
"Forget the Honkai Creatures, I'm more curious about how after all this work, you only reduced the noise by 2 decibels? Didn't you say it would be under 120 decibels?"
"That was the ideal value. There's always a difference between the ideal and reality… With the current materials and technology, achieving this result is already quite good."
Yiselian covered her head and hid behind Himeko, afraid that Ryn would hit her like Emisha would.
"Look at my kind and amiable face. I'm not going to hit you, what are you hiding for?"
Yiselian didn't say anything, just glanced at the mountain-like piles of Honkai Creatures around them and hid even further away.
Ryn was so exasperated by Yiselian's behavior that he laughed and beckoned to her.
"Get back here. If I wanted to hit you, no one could stop me."
"Yes, sir."
Yiselian scurried back obediently.
"Since the experiment is over, let's leave. Hmm? Himeko, aren't you going?"
Ryn and Yiselian were packing up to leave when they noticed Himeko was still standing in the same spot.
"I'm going. I was just thinking… maybe it would be better not to limit the noise and instead turn it into a sonic weapon."
"That's a good idea. It might be possible if we have a safe power amplifier and a focuser."
"Then I'll leave it to you."
"Uh, on the condition that you find me the materials, and also, don't let Bronya find out…"
Watching Himeko and Yiselian chatting together, discussing the possibility of a sonic weapon, Ryn pulled the small cart with the engine system on it and muttered under his breath:
"Instead of a sonic weapon, it would be better to just use it as a monster spawner…"