"Was it okay because it's the sturdiest one?"
"Yeah, thanks. That's a big help."
Eva brought in a large glass box loaded onto a caster.
My private room was a hidden chamber. The trick was simple enough for any Hunter to figure out, but I couldn't very well let outsiders in.
The room I'd intended to be spacious had grown rather cramped with Treasure Weapons piling up everywhere.
Treasure Weapons were both my collection and my actual usable weapons. Putting them somewhere I couldn't reach at a moment's notice would defeat the purpose.
Well, using them didn't make me that much stronger anyway. It was more about the feeling.
I'd planned to have Louke and the others help me rearrange things after they got back, so for now I just set the box down in a corner.
It was an incredibly sturdy piece made from special glass. Used in museum displays and the like, it could withstand a fair amount of Hunter-level force.
I struggled to open the heavy lid and placed the dejected-looking fake Changing Human Face inside.
The expression I'd taken on when I wore it showed no signs of returning no matter how much time passed. At least once my unsettling look had settled into droopy eyes, it was half as bad.
According to what Ark told me, this mask had possessed some young lady and caused a huge commotion.
It supposedly boosted her power enormously, giving her the strength of a mid-rank Hunter or above.
If that was true, this was exactly the Treasure Weapon I'd been chasing for years.
They went by the grand name of Treasure Weapons, but at the end of the day, they were nothing more than tools.
My collection was full of Treasure Weapons that required a certain level of physical ability from their user to be effective. If this mask could provide an easy power boost, maybe I wouldn't have to live my life so terrified.
Just to be sure, I addressed the mask lying limp and lifeless in the glass box.
"Hey, is it really impossible?"
Normally, talking to a Treasure Weapon would be the act of a fool.
But the hole in the mask's mouth slowly began to move in response to my question.
"Impossible. With my power, I cannot unlock your potential. Seek out a higher-ranking mask. Although, if you want to go beyond what I can offer, you'd need a military-grade one with a limited user base whose base body can withstand it—"
Had it been lonely? I let out a deep sigh while watching the unexpectedly loquacious mask.
It seemed this mask had the power to draw out human potential.
And yet, it couldn't unlock mine because my potential was absolute trash.
There were plenty of Treasure Weapons besides this one that required certain conditions from their user, but the implication was clear: my potential was below that of some noble's daughter. Was this world too harsh on me?
I sighed and consoled myself without making a sound.
Disappointing in performance, but its rarity was officially confirmed. A mask that could talk even without being touched—I'd never heard of anything like it. It would probably stop moving once its magic ran out, but it might make for decent company.
Treasure Weapons had their reasons for existing. Though it was hideous to look at, this one too must have been born from someone's need.
Even if it drew out potential, it also seemed to amplify emotions, and whether it was really worth two hundred million Gills was debatable—but since I'd gotten it for free, I had no right to complain.
I'd wanted the Changing Human Face, though.
Eva, who'd been listening to our conversation from behind, timidly chimed in.
"Um... Klye, about that mask..."
"Hmm? Eva, you want to try wearing it? I'd really advise against it."
If Eva wore it and ended up stronger than me, my glass heart would shatter into pieces.
"That's not it."
At my words, Eva looked at me as though I were a lunatic, then said with a sigh of resignation.
"......Could that possibly be a 'Treasury of Knowledge'? I've... never seen one before."
"..."
...Huh?
The moment I heard those words, a shockwave ran through me. I furrowed my brow and took another look at the mask.
The mask was speaking with an indignant tone.
"My name is 'Evolving Demon Mask'—I who advance humanity. To be lumped together with some unknown thing is an insult."
I was an idiot. I collected more Treasure Weapons than anyone, and I hadn't even noticed.
A mask that spoke as if it had its own will. A 'Treasury of Knowledge.' It met the criteria.
Embarrassed, I nodded as if I'd known all along.
"So you figured it out too, huh?"
"Of course—I've studied Treasure Weapons as well. It's obvious once you look closely. ......These should only appear at astronomical odds... I never imagined I'd actually see one with my own eyes—"
For some reason, Eva's expression looked strained. I should have been more moved myself, but I'd missed the moment. I always let things slip at the crucial instant.
A Treasury of Knowledge.
That wasn't the name of a single Treasure Weapon—it was the collective term for a category of Treasure Weapons with a particular characteristic.
Eva took a deep breath and shuddered. She seemed unusually excited.
Her usually calm voice had risen slightly.
"Depending on what's inside, your debt might be wiped clean, Klye. I thought you'd just had one of your usual spells—"
Citry kept saying it too, but calling it an "illness"... wasn't that a bit harsh?
So, do you know what the most expensive Treasure Weapon ever sold was?
A legendary sword that could carve mountains and split the sea with a single swing?
A bracelet that let you fly freely through the sky?
The 'Space-Time Bag' that could store an entire castle's worth of items?
No.
The most expensive Treasure Weapon ever auctioned, and probably the most famous one in all of recorded history... was a book-type Treasure Weapon.
The 'Book of Sand.' Named for the color of its cover, this Treasure Weapon was—an encyclopedia that catalogued every type of Treasure Weapon that existed during the Age of High Arcane Artifacts.
It was likely created at the peak of that civilization. The book itself had no special abilities, but it held information that would overturn everything you thought you knew.
The majority of Treasure Weapons discovered in the Treasure Hall were products of the High Arcane Artifacts Civilization—one of the great civilizations of old, where humanity had flourished thanks to mass-produced, diverse, and powerful arcane devices. And that book revealed the abilities of over half the Treasure Weapons that had been excavated with their identities completely unknown.
Some say the discovery of the 'Book of Sand' heralded the dawn of the Treasure Hunter era.
I don't know where that book is now. But the man who found it sold it and used the money to build a kingdom.
Over a thousand years later, that kingdom had become what we know as the Kingdom of Miel—the largest kingdom in the world.
A fairy tale every Treasure Hunter knew by heart.
A Treasury of Knowledge.
It was the collective term for items that granted their owner information about the civilization from which the Treasure Weapon originated.
Their forms varied widely. Books were the most common, but there were posters, monuments, and more—a mask type might be a first.
This type of Treasure Weapon rarely manifested, but it was immensely useful from an academic standpoint and traded at terrifying prices.
I didn't know how extensive its knowledge was, but for one with enough intelligence to hold a verbal conversation—the price it could fetch was beyond imagination.
This was completely unexpected.
"Two hundred million might have been a steal."
"Even ten times that might have been cheap..."
And on top of that, I hadn't even paid for it.
Most of the information recorded in the 'Book of Sand' had spread over the thousand-plus years since its discovery.
In other words, there was a high probability that this mask was not a product of the High Arcane Artifacts Civilization whose information had already become common knowledge.
If that was the case, putting aside the mask's own capabilities, handing it over to a kingdom would net a considerable sum. Wiping out my debt wasn't necessarily wrong.
I'd gain honor too. The Emperor of Zebuldia was famous for valuing practical benefits. My certification Level might go up, and with any luck, I could even receive a noble title.
...But it was Miss Eclair who'd won this in the auction. Should I give it back?
I recalled the girl whose eyes went wide at the heavenly taste of the Thousand Transformations-supplied cake, and tilted my head in thought.
She'd said she was giving it to me regardless of the reason, so I had no obligation to return it—but if that prideful young lady learned I'd handed over a Treasury of Knowledge for free, I could only imagine what she'd think...
Eva murmured with a serious expression.
"We should negotiate carefully. Should we deal with a trade guild, or approach a noble—or perhaps we should take it to another country. The Kingdom of Miel has apparently been investing heavily in collecting Treasuries of Knowledge for years."
"No, I'm not selling it?"
"......Huh!? I... I thought you went through all that scheming to get it so you could sell it..."
"...Have I ever picked up a Treasure Weapon to flip it for resale?"
I'd bought things at high prices from resellers, sure, but I'd never sold anything.
Having failed to realize it was a Treasury of Knowledge, it was hard to say with conviction, but I was—a Treasure Weapon collector.
Can't use it myself. Could sell it for a fortune. To part with a rare Treasure Weapon for reasons as shallow as those—that made you unworthy of the title of collector.
Eva's eyes went wide and she hurriedly objected.
"......This is too much for one person to handle. It's certainly valuable, but I think you'd be better off extracting all the knowledge you can and then letting it go quickly..."
"That's exactly why this has to be a secret between you and me."
"I think Ark and Lord Gradius already know about it, though..."
True, Miss Eclair already knew that the mask could talk and possessed a high level of intelligence.
If someone wasn't as clueless as me, they might very well have realized the mask was a Treasury of Knowledge.
Ark could be kept quiet. He was a man of little greed or vanity—the very model of a Treasure Hunter.
I thought it over for a while, but in the end I decided to leave it to fate as always. It wasn't like I was doing anything wrong—it would probably work out.
"......Well, it'll probably be fine. In the meantime, send some cake over to Miss Eclair as a goodwill gesture. The carrot-and-stick approach. And don't forget the candles."
"......Understood. ......It's such a rare chance to be free of your debt, too..."
Eva agreed with a hint of dissatisfaction.