The Starforged Sword — Warm Dense Matter

 

「Flack. May I negotiate with Uriel?」

「Go ahead.」

Arthur’s unexpected words were met with a nod from the boy.

「You have no chance in close quarters. Surrender, Uriel.」

「You’re calling for surrender—against a Mythology Weapon? Have you lost your mind?」

Uriel hadn’t given up. He once more raised his sword of flame.

「There is a way to turn you into a Kryptos.」

Arthur’s voice carried a quiet respect—for one who once bore the same burden. Both had been Silhouettes left behind to keep vigil over Typhon.

「I refuse. I have no regrets.」

「I see. Then—Flack, it’s time.」

「Right!」

Flack responded, pulling the hilt free.

There was no blade.

「Fallen angel. Behold—the Starforged Sword.」

What he drew was merely a hilt. No blade in sight.

「Dramatic, aren’t you?」

「Perhaps.」

For a moment, the entire chamber glowed—blindingly bright—as a white blade materialized in the air.

Arthur tested it with a light tap on the floor. A high metallic ring echoed out, and the reinforced floor—reinforced by the A-Carbuncle powering the facility—was gouged open where it struck.

「A retractable sword? Metal reaction detected. Likely a high-grade vibroblade variant.」

「Metal… Yes. They say the sword called Excalibur inspired the word for steel. But there’s another meaning you’ll come to know firsthand.」

「Bold words! Do you claim that this blade is King Arthur’s sacred sword?」

「It is not Excalibur. If it needs a name—call it Caledfwlch.」

Uriel, too, was a top-tier Antique Silhouette, his performance even surpassed Aural. He could not afford to fall to some obscure Silhouette.

「Then I’ll cleave that blade in two. A gimmick sword must have structural flaws.」

「Can you, I wonder?」

Arthur remained unshaken. Uriel’s sword of flame was one of the finest from the Interplanetary War Era—wielded only by the Seraph series.

「Starforged Sword? What’s that, Asia?」

「How should I know? Didn’t you make it?」

「I didn’t make such a thing!」

Kou and Asia whispered to each other, trying to make sense of the unknown term.

「Prepare yourself!」

「Come, Uriel!」

Uriel raised his flaming sword high and charged. Arthur brought his weapon from mid-guard to high stance. Flack’s technique was textbook.

Arthur advanced. Uriel aimed to knock the blade aside before delivering a blow of his own.

Their blades clashed— A metallic scream rang out.

「Wha—」

Uriel’s flaming sword shattered into pieces, and in the next moment, Uriel himself was split clean down the middle—like a bamboo stalk—his body falling in two halves with a final shriek of metal.

「Caledfwlch is one of the many roots of the name Excalibur. It also means ‘cleft’ or ‘fissure’.」

「What… was that cutting power…?」

Uriel’s synthetic voice echoed hollowly. His body, cleaved in twain, never moved again.

◆ ◆ ◆ ◆ ◆

「That was a hell of a strike, Flack.」

「Heh heh.」

Flack couldn’t hide his joy at Kou’s unfiltered praise.

「Bit of a waste, though?」

Matt murmured in disbelief, still stunned by the sword’s power. Uriel had been a Seraph-class Antique Silhouette; for Matt, it seemed like a waste to destroy such a rare and powerful weapon.

「Not at all. He was already contaminated with miasma. Who knows what might’ve happened.」

「Good point. Yeah… But what was that blade?」

「I’m also curious.」

Even Kou was at a loss. He hadn’t thought it was something even Asia couldn’t analyze.

「Caledfwlch, huh? Old Welsh. The root meanings are ‘hard’ and ‘cleft.’ Also can mean ‘point’ or even ‘violation.’ Most likely refers to a rift in the heavens—lightning. It’s said to be connected to the demon sword Caladbolg, too. In that sense… it’s a devouring blade.」

「Exactly right.」

「Hey, Arthur. What is that sword? Unit 5 and I couldn’t even begin to analyze its components. Is that really metal?」

「Asia-sama’s eyes are sharp as ever. That was a bluff to mislead Uriel.」

「You’re really good at that. As expected of a Mythology Weapon from good ol’ Britannia.」

「I feel that wasn’t a compliment. The material is Warm Dense Matter—WDM for short. It’s a highly condensed plasma with metal-like density, controlled by Whis, and only formable under extreme temperatures and pressures.」

「WDM, huh. So the blade itself is plasma…」

A flaming sword was a joke compared to this thing. Even for Asia, this weapon used technology too advanced, the sword was literally—an Another Level armament.

Kou was intrigued too. Arthur didn’t have this weapon when he repaired him.

「Plasma…」

「You know how matter exists in three phases—solid, liquid, gas? Water turns to steam at 100°C, right? But there’s also a fourth phase—plasma. That’s when matter ionizes and electrons get energetic. It’s more common than you would have thought: lightning, fire, and solar flares are all plasma. Still following?」

「Yeah.」

「WDM appears in the transitional phase between solid and plasma.」

「So… it’s like something between plasma and metal? How would that be written in Japanese?」

「There wasn’t a proper term back in your era. Maybe we could call it High-Temperature Condensed Matter. ‘Warm’ in this context doesn’t mean cozy—it still implies millions of degrees. Anything solid you can touch is technically ‘cold’ compared to that.」

「So it’s plasma compressed to solid-like density?」

「More like: it’s a solid being kept intact even as it reaches plasma temperatures. Water boils at 100°C, but under low pressure, it boils at even lower temps. That’s because it can’t maintain its density. Same with metal—it vaporizes at its boiling point. But if you compress it hard enough, it stays condensed even at plasma-level temperatures. That’s WDM.」

「Isn’t that just solid plasma?」

「It’s different. Solid plasma refers to the charged particle behavior inside a metal. WDM is more extreme—it’s like high-energy plasma forced into solid form. I’ll ask Astraea to explain it to you later. I’m sure she will be happy to. Knowing this might give you some ideas for weapon development.」

「Eh?」

Asia had casually handed Kou a terrifying homework assignment. He was now regretting having asked.

「Normally, plasma is very low-density. But if you compress it to extreme levels, like I said earlier, it reaches a phase where it behaves more like metal than any normal metal. That’s why the cutting power is so insane.」

「Can that really be done?」

「On Earth, it was confirmed theoretically. Observed it briefly—on the picosecond scale. But it instantly transitions to liquid or gas. WDM is even rarer than metal hydrogen, and the challenges to produce and study it were even greater. Only an Another Level Silhouette could produce that kind of energy.」

「Correct. It consumes massive energy and can’t be sustained long. The pressure needed is comparable to the pressure inside a gas giant’s core. Think of it as an evolution of metal hydrogen. This sword is a trump card even for an Another Level Silhouette.」

The blade had already vanished from Arthur’s hand.

「Another physics-breaking material, huh…」

「Like I said, plasma density varies with pressure. Remember old fluorescent lamps from your time? Those things had a color temperature of 5000 Kelvin. Sounds crazy hot, right? But in reality, the gas inside was only around 70°C. WDM needs pressures equal to those inside a planet core. That’s why it’s called the Starforged Sword.」

「So it needs even more pressure than metal hydrogen.」

「Exactly. Jupiter has rivers of metallic hydrogen on its surface; inside the planet metals much denser than those on Earth exist. Arthur’s armor was probably made with these materials. Inside the core, the material is even denser, and the material of the core is believed to be WDM.」

「The fact that Argus and Steropes managed to restore that thing is insane.」

Kou’s authority meant little when it came to restoring an Another Level Silhouette. Even as an EX-rank Development Engineer, the technology he could access was limited to technology from the Earth era and their applications; this hadn’t changed even after Asia had partially lifted the technology restrictions. He couldn’t replicate tech from the Pioneering Era.

「Ordinarily, it would’ve been impossible. But wisdom gathered, Outis.」

「Wisdom…?」

「The mobile Arsenal Platform Astraea-dono, and her sister Eirene. Morgan, the Lady of the Lake who commands Realm. Arges-dono, Steropes-dono, Polymetis-dono… and one unknown collaborator. This last person’s identity remains a mystery.」

Asia and Kou fell silent. Only one person came to mind—Arima. Morgan must already know.

「And we were lucky to have Abel—our own Merlin. He examined records from his homeland and succeeded in reviving plasma-based fusion technology.」

「What’s Britain got to do with fusion?」

「The world’s first fusion patent came from Britain, Kou.」

「…Britain, huh.」

「Don’t say it like a sigh. It was a remarkable achievement.」

「I thought it was the U.S.」

「The theoretical groundwork was completed in the 1920s. A British physicist, Francis Aston, proposed it as the Sun’s energy source. After that, the UK and US collaborated closely. It was during that research that helium-3 and tritium were discovered.」

「Britain and fusion… Never had that image.」

In Kou’s time, Britain was mostly seen as a financial hub.

「Asia, tell me—are Another Level Silhouettes powered by an A-Carbuncle?」

「Probably. But I don’t know for sure. Even in the Pioneering Era, I didn’t have access to technology to miniaturize an A-Carbuncle that far. That’s beyond our jurisdiction too.」

「Figures. Astraea didn’t know the details either. We haven’t disassembled Yōnātl Tepatztl’s power pack yet.」

「Wise move. It’s best not to mess with things like that.」

Then Kou turned to Arthur with a sudden realization.

「You know… why not just call that thing Excalibur already?」

Arthur had once insisted on naming his positron cannon ‘Excalibur’.

「Eh? But… the positron cannon just looks more dramatic. That trail of aurora… hard to give that up.」

「So it’s about the aesthetics!?」

Realizing that Arthur wouldn’t name the WDM blade Excalibur because of how it looked, Kou couldn’t help but shout.