"(What the hell did you do?)" asked the person projected onto the display, who was not the Gregory Charles I was used to. Not because Gregory was unavailable at short notice this time, but because I'd apparently neglected my geology. Now Gregory wouldn't be available at any notice, having been forced to resign by the weight of public outcry. His choice to let me test the monster-core-powered light crystal had backfired on him badly.

The bomb could erase a town, Grover had said. What was the radius of an average town? A kilometre or two? Or perhaps it did somewhat more, given that he'd said not to use it within ten kilometres of a person. I had no idea how much of a safety margin he'd left in with that request.

But whatever its precise range, the important fact was that decay grenades produced a spherical field, which meant that however far it struck sideways, it also drilled down.

And if the bomb happened to go off in an underground bunker that was already a kilometre down, simple maths required that the depths be summed together.

And if that bunker had been positioned where it had been for ease of access to plentiful geothermal energy, indicating high rock temperatures very close to the surface, then erasing a chunk of bedrock multiple kilometres deep had a decent chance of hitting a magma pocket.

Still, it could have been worse. I could have blasted clean through the crust and into the mantle. As it was, the volcanic eruption caused by the decay bomb wasn't even the largest recorded on Earth in the previous century. It wasn't even by that large a margin with which it was the largest of the decade.

"(I threw a supercharged toilet through the portal,)" I answered.

"(This is not the time for jokes,)" he snapped. "(Even if you didn't foresee breaking open a magma pocket, was that really a proportionate response to a simple intrusion? Do you know how many voices are screaming about how dangerous your world is now, and how we should 'pacify' you? And this is before they find out about the Law!)"

"(It wasn't a joke, and it wasn't a simple intrusion. We don't really do large-scale weapons over here, so when they started flooding the continent with plagued rats, I had to improvise. It really was a weaponised toilet.)"

"(... What rats?)"

"(On our last contact, I mentioned they had thousands of rats lined up in the portal chamber. Well, this time we found out what they were for. Disease carriers. They opened portals in rapid succession, sending a pack of rats through each one, which in turn infected anyone nearby with... hell knows. Something unnatural cooked up by that Maximilian, most likely. Even with healing magic, there were deaths, and there was no way we could let it spread further. We shut them down in the most expedient, safest way we could.)"

"(Safest?)"

"(Decay crystals very thoroughly destroy everything in the vicinity, without causing any harm at all to anything outside their active radius or leaving behind anything toxic or radioactive. We didn't know what size facility we were dealing with, so we had to guess at the payload size.)"

"(Well, congratulations. You successfully destroyed the facility. You also buried or burned hundreds of square kilometres of farmland and destroyed an entire town and multiple villages. So much for not causing harm outside of its active radius.)"

"(At least you know who was responsible now.)"

"(How can you be so flippant about this?)"

"(Oh, believe me, I'm not. I've been completely torn up ever since I did it, wondering how many lives I took and how many of them were innocent. Thankfully, you getting angry at me for defending this world against a literal genocide attempt helped me snap out of it.)"

"(And do you have any evidence for this 'genocide attempt'? Or any suggestion of a motive?)"

"(Evidence, no, because we burned everything that was infected, including our own corpses.)" And we really had; I'd explained how some things could survive being frozen, and Krana had run a second pass over everything, including the dead centaurs. "(Motive? Short term, it would cut off the supply of monster cores to you. Perhaps they think they can harvest them themselves with the aid of drones or isolation gear. If they have a genius biologist on their side with knowledge far beyond Earth's, they probably think they can come up with vaccines against our local pathogens, and in the longer term repopulate our planet themselves.)"

"(So no evidence, and only baseless speculation.)"

I was going to have to take back everything I said about Erryn's Peter-can-lie patch to the Law. However much I complained about it, that only affected the little things. The natives wouldn't dream of disbelieving me about something as serious as this, but here I was, having to justify defending myself against someone trying to wipe out all life on the planet.

"(So what do you think we should have done? Politely ask them to please stop murdering us? Carefully preserve corpses infected with goodness knows what, putting ourselves at further risk just so we can justify ourselves to other residents of your planet who weren't even involved?)"

"(Given how quickly you dealt with it, it obviously wasn't the existential threat you're making it out to be.)"

"(Oh, come on. Even I know more about epidemics than that. They're fairly easy to contain if you catch them early, when there's only localised infections. If it had spread, we'd have lost control of it very quickly.)"

"(Regardless of whether this disease is real or not, the fact remains that you've caused a very public catastrophe on our world. We're suspending our trade agreement.)"

I blinked, astonished. That would harm them far more than us! We'd stockpiled so many textbooks, research papers and random bits of tooling and equipment now that with our low available manpower, we'd take decades to make any sort of dent in it. Meanwhile, they were getting a source of free, clean power, but one core wouldn't last forever; if they built power plants around them, they'd need a continuous supply of fuel.

He had said 'suspend' rather than cancel. Maybe they had enough for now, and expected to resume before they ran out? Or maybe they didn't want to make themself dependent on us in the same way they were dependent on others for oil and gas; if they relied on the monster cores for national power distribution and we suddenly stopped supplying them—to pick a random example, because we'd been wiped out—they'd be in trouble.

Maybe they were already turning against us because of the System encroachment and threat of the Law, and this pushed them over the edge. Maybe they wanted a third party to kill us all, so they could save themselves while maintaining the moral high ground.

I sighed, trying to expel such thoughts. Just like their complaints against me, I had no evidence for it. It could just be a simple matter of the general public being against trading with people responsible for burying hundreds of square kilometres under a layer of lava and ash, and this guy trying to preserve his chances in the next election.

"(I don't think we have any complaints about that,)" I agreed. "(Frankly, I would prefer to completely sever our worlds, so that our paths could never cross again, but alas, I suspect that's no more possible than it would be for you to build walls around your borders. So where does that leave us? We still need to trade intelligence.)"

"(I don't believe we do. If someone else encroaches on your territory and risks your reprisals, that's their own fault. You've made your opinions pretty clear. We intend for this to be our last communication. If you open another portal here, we shall treat it as an attack.)"

"(What?!)" exclaimed Abigail. "(But we want to go home at some point!)"

"(You're already infected. By their pathogens and by their System. You can never return here.)"

"(And what do you intend to do about your children?)" demanded Harry.

"(That's our business, not yours. Now, I believe that we're done here. Please close the portal, before we do.)"

The heck? None of the six earthlings looked too perturbed by being abandoned, having acknowledged the risk from the beginning, but none of them looked happy, either. At least up until now, they'd been able to send messages to friends and family. Now they were completely cutting us off, which was kinda what I wanted, but I wanted it to be a physical barrier, not just them deciding to.

I'd never dreamed they'd wilfully kill their supply of monster cores forever. So much for 'suspended'.

Maybe they weren't. Maybe they'd found some side effect that rendered them unsuitable as a power source after all, or maybe they had their own nefarious plans. Heck, for all I knew, the guy was in league with Maximilian.

"Go on then, kill the portal," I told Darren, and he did, severing us from Earth for what I doubted was the final time, however much both sides apparently wanted it.

"What the hell is he thinking?" demanded Cara. "That's not just catering to public opinion. If they kept occasional contact, who would ever know?"

"If they wanted to keep it quiet, they wouldn't be able to pass messages on from us," pointed out Calvin.

"True, but beside my point. We've already proven that when someone starts messing with portals, we pick it up on our side faster than they do. They're cutting off a vital intelligence source."

"I recognised that guy," chimed in Russell, the guard making a rare interjection into the conversation. "He was part of one of those anti-wormhole groups... Which one?"

"Some pretentious, single word thing. Sunbeam?" tried Dominic.

"Aye. Could be."

Sheesh. How many were there that they were mixing them up?

"Oh, I remember them," said Abigail. "They've been around for ages. They were pretty heavy believers that the LHC was going to produce miniature black holes which would eat Earth."

Harry clicked his tongue in annoyance. In my opinion, any group would have a good point claiming that poking holes out of their universe and into another might not be the safest thing in the world, but it did kinda complicate matters. As if they weren't complex enough already.

"I remember them too," said Calvin. "They were... misguided, but made logical arguments. I can't imagine him cutting us off without having a plan to deal with the System and Law encroachment."

But what could they do on their side?

... He'd just told us to close the portal before he did it for us.

"Harry, with what you know about Darren's portals, could you close one from the Earth side?"

"There's a few things I could try. But the way they stabilise after being open for a while... It might only be possible if I did so immediately."

Had that been bluster or a legitimate threat? If Harry couldn't think of a way to do it, then how could anyone on the other side? They didn't have portals to experiment on. Having knowledge of how to shut down a portal would imply they had knowledge Harry wasn't aware of. Perhaps they'd been working with Maximilian, or they'd found another portal research group without admitting it.

Or the third option was that he didn't have any specialist knowledge on how to close portals, and would have just piled bombs through.

Hmm...

"What about detecting portals?"

"Definitely. All portals, ours and yours, produce an easily identifiable EM signature."

"What frequency EM? How transparent is Earth's atmosphere to it?"

"Very. And yes, it could be detectable by satellite, if that's what you're thinking... From your questions, you're theorising that they're planning to track down the portals opened by the System and destroy them?"

"Yes, which is fine. But if they don't actually know how to close portals..."

"Then they'll 'close' them with their equivalent of your supercharged toilet," said Harry with an unwelcome smirk.

Damn...