Incursion team mobilizes at Site-574 at 0500 hours. MTF Chi-5 Team Two and MTF Zeta-9 Team Four each drive AFVs, for use in encounters with additional SCP-3667-1v or other SCP-3667-1 instances. The remaining four teams travel on foot. An additional MTF personnel, henceforth referred to by her designation Perevodchik, provides translation between MTF Chi-5 and MTF Zeta-9; unless otherwise specified, Perevodchik’s translations are omitted from the log for sake of brevity. All MTF personnel have been armed with ordnance and small explosives, in addition to antidemonic kinetics and incendiary devices stored in the vehicles.

Echo: Mole Team Two, reporting in – hey, P, is Command one of ours or theirs?

Command: I’m not sure what you mean.

Perevodchik: Command is local.

Echo: Huh. I’d prefer someone I don’t need a translator to understand, but… P, tell Command we’re here.

Juliet: Z-9 Team Three. We’re all here.

Anna: Quite a party today, isn’t it, Command? A shame we’ll all need Perevodchik to communicate.

November: Better hope it’s a quiet trip today, then, P. Otherwise these boys and girls will be crowding all over you.

Perevodchik: I guess that would make me something of a celebrity, then. I always wanted to be a VIP.

(Laughter.)

Konstantin: Team Three here.

Yelena: And last but not least. I think that’s everybody, Command – are we cleared to go?

Command: You’re cleared from up here. Proceed when you’re ready.

Konstantin: Alright. Zeta-9: before we enter the anomaly, I just want to warn you that there’s a bit of disorientation when you cross over. You’ll feel dizzy…

Oscar: Dizzy, a little nauseous, everything’s dark and you lose contact with Command for approximately three point zero five seconds? Yeah, we’ve been there, done that. It’s bog-standard for dimensional skips like this. Besides, we’d already read through all your exploration logs by the time we touched down. We know this place inside and out.

Foxtrot: SSUDS2. Stable, Stationary, Unaided, Delayed, Safe, Two Way.

Gregory: I knew that.

Oscar: In any case, here’s the plan once we get inside. Lima here’s run analysis on the interior schematics of this place and determined that most of the larger stone structures tend to congregate around the river systems. That’s where we’ll find the big critters. Each team here will take a major river – I trust you know where they are by now – and clear it out, end to end. If you need backup, radio one of the teams with the van. Command will be looking out for you as well, assuming you speak their language. Questions?

Vasily: I wasn’t aware we had discussed this.

Oscar: The other Moles and I came up with it on the plane ride over. Given these entities’ behaviour, it’s the best strategy if you want to keep this clean and quick.

Konstantin: With all due respect, I don’t think you know this place like we do. Chi-5 – we’re all Mirny boys and girls. We grew up around the mine. We were there when things started coming out of it, and we’ve been down there forty-odd times by this point. We can handle ourselves.

Oscar: With all due respect, I don’t think you can. I’ve watched the tapes. I’m glad to see your ankle’s doing better, Gregory. Be careful on those hills, won’t you?

(Twenty seconds of radio silence.)

Oscar: Look, I’m sorry. I know this is your home turf. But you’ve got to trust us on this one. This is what we get called in for.

Yelena: Command?

Command: Go on ahead, Oscar. Let’s get this over with.

(Incursion team enters SCP-3667 without any further incident. As per Oscar’s instructions, each team is assigned to a major river system and begin a sweep for hostile entities. The rats observed near SCP-3667-3 instances are more present, being sighted by several teams; however, none approach personnel.)

Juliet: These rats a 3667-1?

Zhenya: We’re pretty sure they’re just normal rats. There’s not as much weird shit in here as you’d think.

Lima: Where’s all the creatures, then? They’re sapient, aren’t they?

Vasily: Some of them are. Most aren’t.

Oscar: We’ll find the non-sapient ones wherever they happen to be. If it’s the sapients we’re after, though, they might be coordinating… ahh, there’s one.

(Aggressive gibbering and the noise of antidemonic kinetics being fired can be heard.)

Oscar: Squishy little fuckers, aren’t they?

November: There’s some in your hair.

Oscar: What’s that?

Perevodchik: She’s saying the coast is clear.

Oscar: Ever seen one like that before? Weird little guy, drinking out of the stream. Looked like a skinny little kid with a big, drooping head. Is that one sapient, do you know?

Boris: Sounds like a 3667-1m. Sapient, but just barely. I wouldn’t lose any sleep over it.

Yelena: That’s one monster down out of… what, hundreds? There’ve been times where we couldn’t walk around this place without sneezing all over a colony of 3667-1-whatever-the-fuckers. Where did they all go?

Oscar: Chi-5, how many of these rivers have you explored end-to-end?

Konstantin: The big ones, you mean? Uh, most of them. I’d say… 80%.

Oscar: (Opening supply packs in AFV.) There’s a map of this place in here somewhere, isn’t there? Here. Konstantin – it’s Konstantin, right?

Konstantin: Yes. Why are we stopping?

Oscar: If I showed you the rivers, here, on a map, would you be able to point out the unexplored ones?

Konstantin: These… three. Yes, I think that’s all.

Oscar: That’s Zeta-9 Teams Two and Three, Chi-5 Team Two.

Konstantin: Chi-5 Team One.

Oscar: Right. You’re right. Moles Two and Three, Chi-5 One, come in. What’s your position?

Juliet: This is Team Three. We’ve reached the end of the river. It all drains into a sinkhole – we’ve thrown a couple of torches in, but the bottom’s pretty shallow. Honestly, Oscar, I don’t think there’s anything here.

Echo: Mole Two here. When we got your message, Foxtrot scouted out ahead, and he says the river goes into a crack in the wall the size of a mouse. Too small for us, or anything else here, to squeeze through. We haven’t seen a single creature on our whole jaunt so far.

Konstantin: How about you, Team One?

Gregory: We, uh, we found a cave.

Anna: Konstantin, the river flows through a passageway here that leads into a chamber… it might be bigger than the one you’re in now. There’s a lot of artificial activity present here. Bricks in the walls, bones and garbage – we found a couple of 3667-3 instances, but no people in them so far. Vasily keeps saying he can hear noises up ahead.

Gregory: It’s a really big cave.

Konstantin: You think that’s it?

Oscar: Definitely. I’ll call the other teams to rendevous at – well, here, you do it.

Konstantin: That’s not necessary.

(Two minutes of silence.)

Oscar: Look, we’re sitting in a cave in Hell in Russia, and I don’t want to have to ask again.

Konstantin: Thank you.

Oscar: I’m not staying in here any longer than I have to.

Konstantin: Zeta-9 Teams Two, Three, Four, Chi-5 Teams Two and Three, we’re rendezvousing at Team One’s location. I want everyone there in five minutes, tops.

Yelena: Understood.

Echo: On our way.

Konstantin: What do you think we’ll find in there?

Oscar: I don’t know. Nothing good.

Konstantin: Anna, hang on and wait for us. We’ll be there soon.

Anna: The river looks different here. It’s… bubbling.

(Chi-5 Teams Two & Three and Zeta-9 Teams Two through Four rendezvous with Chi-5 Team One without further incident.)

Yelena: Anyone seen any creepy-crawlies so far? We haven’t.

Juliet: I think it’s just Konstantin and Oscar who have.

Anna: Command, are you getting this? I don’t know if this river’s made of the same stuff we sampled before.

(River appears milkier-white than previously and gives off a small amount of heat. Bubbles previously observed by Anna appear to be small handlike structures that spontaneously form and recollapse as they flow downstream.)

Dmitri: That doesn’t look safe.

Konstantin: Dmitri, hand me a pole from the truck. I’m going to test it.

(Konstantin retrieves a telescoping pole from the AFV’s supplies and inserts the end into the middle of the river. When lifted, the submerged section of pole is missing entirely.)

Konstantin: Alright, I want everyone as far away from the river as possible. We’ll –

(There is a slithering sound and a large leech-like creature, classified as SCP-3667-1h, drops from the ceiling of the cave and engulfs the upper torso of Oscar, who is standing nearest to the river.)

November: Shoot it! Shoot it!

(Before any members of the incursion team can reach it, the SCP-3667-1h instance flops into the river, where it and Oscar are carried away by the stream. The instance appears impervious to the river’s acidic contents, but Oscar’s extremities are observed sloughing off and dissolving into liquid. Where his skeleton is exposed to the river, there are several seconds of resistance before it, too, melts into a thick white paste. The SCP-3667-1h instance shakes itself free of what remains and swims further down the river, and November chases after it, showing signs of distress.)

November: (Sobbing.) You fucking bastard, son of a bitch!

Juliet: November, wait!

Konstantin: Dmitri, Juliet, grab the trucks. We’re following him.

Juliet: Are you sure? I don’t think –

Konstantin: No one else is going to die. I can’t… I’m not going to let that happen.

(The remainder of MTF Chi-5 and MTF Zeta-9 follow November, who continues to vocalize distress. The surrounding environment begins to brighten by degrees, but the incursion team does not take notice of this until November loses his footing on an outcropping of rock and stops.)

Boris: Holy hell.

November: That’s, that’s where all these bastards have been, been fucking hiding.

(Approximately 1km ahead of the incursion team’s location, a large complex of stone structures several stories tall is visible, lit by enormous metal braziers that are responsible for the increased illumination. The complex straddles the river, and as the operatives watch a complicated wooden mechanism above the river appears to release several SCP-3667-2 instances, which quickly dissolve.)

Zinaida: I thought we got all the people out of here.

Gregory: Look. Over the river.

(An elaborate system of what appear to be wooden walkways crisscross the river, on which are perched several SCP-3667-1a and SCP-3667-1b instances. Millipede-like creatures approximately 30 meters long, classified as SCP-3667-1w, periodically climb from the river to the walkways or vice versa. All sub-instances occasionally reach into the river and extract a quantity of liquid, which slowly solidifies into a SCP-3667-2 instance: this is then consumed. Other SCP-3667-1 instances are observed excreting fully formed SCP-3667-2 instances back into the river, where they are dissolved again.)

Yelena: (Breathes deeply.) Okay.

(Gregory retches. Although the incursion team continues to observe the entities and their prey, Oscar does not reappear.)

Konstantin: Alright, that’s it. We’re going to finish this, and we’re going to finish it now.

November: We… we can’t. There’s too many of them.

Konstantin: They’re eating out of the river, right? All eating, like the happy fuckers they are. Well, we’re going to let them keep eating as much as they goddamn please.

Dmitri: Are you sure about this, Konstantin? This isn’t in the mission parameters.

Konstantin: Mission parameters got someone killed. I want everyone’s antidemonics on the ground here, and we’ll need the extra drums from the truck.

(All antidemonics and refill fluid drums are assembled. Konstantin rolls one of the drums to the edge of the river and begins to pour it in.)

Konstantin: No one’s going to die. Except for those fuckers.

END LOG

After-action reports estimate that the introduction of antidemonic solution into the SCP-3667 river system led to the termination of over 80% of the anomaly’s native inhabitants, with the exception of SCP-3667-2 instances. MTF Chi-5 Team Three Captain Konstantin subjected to internal review for unorthodox actions taken in the field, but was subsequently commended for fulfilling original mission requirements without a severe loss of life. SCP-3667 tentatively reclassified to Euclid.