"You know the quarantine ended this morning, right?" I asked Harry, who was frustratedly watching Grover cut notches into a disk. Without crafting skills, there was little he could do to help other than providing knowledge, but he'd nevertheless been doggedly at this for the past few days. He might have refused to start researching portals before talking to my parents, but that didn't mean he was forgoing science completely.

The experimental setup was apparently a well-known one on Earth, which made me feel a bit clueless; I'd certainly never heard of it. Something about shining a light at a mirror far in the distance, with a spinning cog between the two. Or shining a dark, in this case.

Meanwhile, Cara was staring at a wooden box, fidgeting. Unable to resist temptation, she lifted the lid a fraction.

"I need to be able to see what I'm doing, lass," called Grover when the rank four darkness crystal inside made its presence known through the crack, plunging the room into darkness. Vargalas had happily provided us with one after mine were declared too weak for their purposes.

"(It must be undergoing diffuse reflection, or it wouldn't have affected the entire room like that,)" observed Cara. "(Only the bits directly exposed.)"

She'd phrased it in a more technical way, but I'd made the same observation back when I was first giving a lesson about lenses before the institute existed.

Over the past few days, both Cluma and I had quickly realised that our translation abilities were imperfect. A level ten in both skills apparently did nothing to familiarise myself with the technical terms they kept throwing around. Thankfully, their levels of [Language: Common] were shooting up as they did their best to comprehend what people said around them. It was already at the point where I only translated for them when asked.

I left them to it, instead carefully placing my decay crystal into its socket while employing [Expert Mana Control] to keep all the mana as far away from it as possible.

ding

Skill [Expert Mana Finesse] advanced to level 18

Yay, the skill was maxed out once more. That was a forty-three percent decrease in all mana costs, before adding in the effects of my enchanted jewellery. Mana had basically become a non-issue and short of me getting some seriously mana-hungry spells, maybe at rank four, I'd never need to worry about it again. I'd given serious consideration to keeping [Minor Speed] up at all times, and had only decided against it because I suspected it would speed my ageing.

Anyway, with the quarantine lifted, I could head out to the fields to conduct an experiment of my own. What would weaponised decay crystals do?

I left the proper scientists to their speed-of-darkness experiments and made my way to the usual field, Cluma stalking along behind me to ensure I didn't get any stupid ideas about testing it out on myself.

"Shouldn't you be translating?" I asked.

She gave me a Look, part of which was directed at the apple-sized device in my hand. "No," she answered flatly.

"I'm hardly going to blow myself up!"

She continued to stare.

"... on purpose," I added, when she didn't stop.

"Those things eat through the floor if you don't put them on a proper base! And you turned one into a weapon!"

"And a fire crystal would set the floor on fire. Not really much difference. The crystal will break when I activate it, so it's probably not going to do as much as you're worrying about."

"Why not an ice crystal? Or even a light crystal; make something that flashes so bright that it blinds monsters."

Despite Cluma's opinions, I wasn't completely foolhardy, so rather than throwing the thing, I carefully set it down on the grass before retreating to the maximum range of my [Expert Mana Control]. Ensuring Cluma was safely behind me, I triggered the device.

There was hardly any noise. No explosive bang or loud clap. Just a quiet, low-pitched hissing, like radio static on the edge of my hearing, as five metres of surrounding field came apart. Chunks of soil and greenery rose gently into the air, gravity be damned, breaking apart into progressively smaller pieces until the grenade was surrounded by an orb of dust. Or rather, former grenade, given that it had disintegrated too. The dust became finer and finer until it vanished completely, from both my sight and [Mana Sight]. The cloud of complex affinity faded away a few seconds later.

ding

Skill [Advanced Runecrafting] advanced to level 9

"... Wow," opined Cluma.

"Yeah," I agreed.

"What would that do to a monster?"

"One way to find out."

"Later. Wait until your guests are settled in."

Yes, that would be advisable. Didn't mean I had to completely give up on the train of thought though, so while the intelligent bunch prepared to measure the speed of darkness, I made a bunch more decay grenades, along with ice, light, dark, water and lightning varieties.

ding

Skill [Advanced Alchemy] advanced to level 4

Class [Artisan] advanced to level 8

Class level increased dexterity by 1

Class level increased intelligence by 1

Water proved, as expected, unimpressive. It would make a cool weapon in a water fight. Not so much in a real fight. Lightning was, surprisingly, equally boring, discharging instantly into the ground and leaving little more than a patch of burnt spoil beneath it. It could be useful if I had a more accurate trigger and could detonate it in mid-air with perfect timing, but without that, it would be mostly useless.

I was expecting light to be more effective than darkness, but surprisingly, they were evenly matched. A sufficiently intense burst of darkness turned out to leave blinding after-images every bit as bad as a bright flash of light. Another small data point for the others as they measured the properties of darkness.

Ice behaved like I'd expected, freezing a patch of ground. It could be of use against monsters that were particularly vulnerable to the element, but it didn't have the coolness value of a decay grenade.

"Think you can refrain from blowing anything up for a few minutes, lad," called out Grover behind me as I was examining the frozen patch. On closer inspection, it went quite deep; the grenade had frozen a perfect sphere, despite the earth in the way.

"Strictly speaking, I've not made a single explosion today, but yes, I'm done."

Grover looked around, taking in the circle of frozen ground, the small scorch mark and the hemispherical crater from the decay grenade, which was simply missing rather than exploded.

"You built a bomb from a decay crystal, didn't you?" he accused.

"Maybe? Is that bad?"

"Let's just say I'm glad your skills are still only second rank."

Dammit. Now I wanted to see a combo effort between him and Vargalas. Preferable from a safe distance.

Grover was carrying the giant cog over his head, the Earth scientists trailing behind him. As I'd already noted, just like the way they lacked crafting skills, they equally hadn't yet had the chance to boost their strength to superhuman levels, and were no help moving equipment around.

He hoisted it onto a frame and connected it up to one of Vargalas's lightning crystal powered motors, rather than one of his own, presumably because it span at a more controlled rate. A light crystal—since they wanted to measure the speed of light before checking how darkness behaved—went into a box of mirrors and lenses that did a pretty good job of turning the three-sixty degree output into a tight beam. A silver mirror made up the last part of the apparatus. Grover and a few helpers carefully set everything up in a neat line, rotating the cog by hand to prove it blocked the beam.

"(The cog and mirror need to be further apart,)" recommended Harry. "(Unless the speed of light... or darkness... is far slower here, you'd have to spin it far too quickly to be viable.)"

What would make it non-viable? Vargalas might be a bit crazy about lightning, but I didn't doubt the performance of his creations. Likewise, the stuff that Grover made...

Mana reinforced steel gear (Quality: 52)

- Enchantment: Durability (Quality: 84)

Weight: 200 kilograms

Yeah, that wasn't going to break. Given the quality rating of the enchantment, there must be mythril or orichalcum in there too, despite [Eye of Judgement] not showing it up.

Grover, not having a clue what Harry had just said, switched on the engine and started playing with a bunch of gears. The larger cog span faster than I could see, but I could see the light-beam impacting a panel next to the crystal. It flickered on and off as the cog's speed varied.

"Looks like it's working to me," I commented.

Harry stared at the engine and apparatus it was all connected to. "(How the heck is that holding together? It must be spinning well over ten thousand times a second.)"

"(Rank five durability enchantments.)"

He just shook his head in exasperation before joining Grover to engage in some maths. It wasn't long before he declared the speed of light here to probably be the same as back on Earth. The experiment wasn't particularly accurate, but it was good enough to get an estimate, and the estimate overlapped with what they expected.

I was fairly sure changing the speed of light would have interesting knock-on effects, of the sort that would mean that the Earth bunch wouldn't have been able to cross through the portal in one piece, so so far, so sensible.

With that settled, they replaced the light crystal with the darkness one, casting a very nonsensical spot of shadow onto the white panel. It wasn't long before they declared the speed of darkness to match the speed of light.

"(Now you just need to figure out how the heck it works,)" I laughed, as their exasperation only grew. "(There are no such things as anti-photons, are there?)"

"(It would be more accurate to say that photons are their own anti-particle. I can't imagine a change to reality that would make that no longer true without being every bit as disruptive to human life as a change to the speed of light.)"

"(Has Cluma ever shown you her invisibility skill? She can make herself completely invisible, but can still see perfectly well. Maybe related?)"

The Earth scientists turned to look at Cluma, who vanished. "(What?)" asked Harry, but in an automated sort of way, and he obviously wasn't expecting an answer.

"(Okay! We can solve this!)" exclaimed Cara, clapping her hands. "(Cluma, does that skill make you feel hot or cold at all? Do you overheat if you keep it up for too long?)"

"(Uh... No? I can't feel it at all,)"

"(My theory is that she's not really invisible at all, and the System messes with our perceptions.)"

"(Drat. Should have tested it while we were disconnected. We've never seen a darkness crystal while disconnected, either... So the entire thing might just be an illusion?)"

"(Darkness affinity has been around for longer than the System. I think. I'm pretty sure affinities have never changed. And Cluma can cast some darkness spells, too. It's a pity Darren doesn't have darkness affinity, given that his magic doesn't come from the System.)"

"(Huh? What does he do then?)"

"(No idea. No-one else can copy him.)"

"(Maybe we're all trapped in a virtual reality?)" suggested Abigail, which made me smile a little since that was one of my theories before Erryn deigned to speak to me.

"(How would we have got into it, though? We crossed through a portal.)"

"(Maybe Earth is part of it?)"

"(A viable theory, but not one that's falsifiable.)"

That had never been part of my own suspicions. Fakery all the way down. Where would the real world be? Was there one at all?

"(Nothing is falsifiable. We all have an alien computer in our heads, able to alter our memories at will. We can't trust anything we see or think we've seen in the past.)"

Harry swore.

"(Well, we can't just roll over and give in,)" said Calvin. "(We have to proceed assuming there's some underlying, discoverable logic to the world.)"

"Sorry to interrupt," called someone I'd seen before at the reception desk, jogging over to our group. "There's a group of harpies at reception. Apparently you're expecting them?"