What do you think happened on the fourth exploration? I think they sent an armed team down there with guns, food and tents and when they finally reached the bottom, they awakened some sort of monster that killed them all.

The beauty of it is that it is entirely up to the individual to fill in that gap.

My best guess is that they sent in a more specialized Class-D, someone with experience or just more mentally stable and calm. Maybe he got very far down, maybe even to the bottom.

I love the fact that the article makes several nods to the fourth exploration and hints to what the aftermath brought. I'd consider they did something much more different compared to the other explorations.

Perhaps they took the short route and lowered a camera via pulley and actually received footage, but agitated 087-1.

It is obvious that whatever happened on the 4th exploration caused this entity to move towards the front entrance, whether it was forcibly trapped in there or attempting to lure more people in however is a mystery.

Also something horrible must have been discovered within SCP-087 to cause the Foundation to permanently stop anyone from entering it again, especially since the front door is held shut in an extremely secure way. Maybe the people are being used for an unknown purpose.

SPECULATION TIME
This entity leaves behind a mucus like substance in areas it has been stationery on for an extended period. It is also a very powerful entity due to it's ability to easily destroy concrete with ease, it is also somewhat fast as it can rapidly close a distance in seconds, as well as keep a consistent distance between itself and a target even while the target is running away.

The entity's body has most likely placed its face far forward from the body, this means that its full body can be hidden in the darkness while only exposing its face to a target. In certain circumstances this could confuse the target to move towards it, making for an easier attack.

However the entity seems to not attack a target in any viewing of it, while there are indications that it has attempted to attack a target it never does so, at least while "on camera". This could imply it does not want to damage or kill its target but incapacitate it. This leads to another theory about the staircase, if we assume the entity wants to capture its targets, then having a staircase that can lure someone down it for a massive distance, if not kilometer's, would be invaluable. This would allow it to trap a target within and tire it out as the target attempts to evade the entity.

It would seem that the entity is slow to acquire a potential target, as shown in Exploration 2 it was heard slowly approaching the target, most likely attempting to ensure the target, but this allowed the target to escape from the staircase. This could reinforce the assumption that the entity needs to tire out it's target first before it is capable of capturing it.

On the lure subject it seems that the pleas for help coming from the staircase are a lure mechanism created by the entity to lure targets into it. On exploration 3 the sounds of the pleas get louder as the entity gets closer to the target until the sounds are almost on top of the target.

The events that occurred on the first two explorations may have been the entity's attempts to figure out the best methods of capturing target's. It would have learned that as soon as its presence was revealed the target would retreat back to the surface. To overcome this it decided on the third exploration to instead trap the target by moving behind the target, cutting off it's escape attempt and force it further down the staircase. How it got behind the target however is interesting, the methods used could be.

1. It hid behind the entrance and followed the target from there.
2. It is capable of cloaking or hiding from vision.
3. When the target was preoccupied with looking down the "hole" in the ground it took the opportunity to sneak behind the target, which makes sense.

There is a lot more to discuss, but I will leave it here for now.

I found it especially eerie how it was mentioned that students and staff on the campus could hear occasional knocking coming from inside the well weeks after the last exploration. It'd be most certainly unnerving to come to realize that for the those working on 087.

Indeed an interesting point Ominary, also I just added a big speculation post to my prior post.

Hmm, most interesting I find about 087-1 itself is its luring mechanism. I always imagined the entity moving much further on past the face, which is just, more or less a smaller manifestation, which, in the 3rd log, was used to lead the subject deeper into the stairwell, effectively trapping them. It's usually a giveaway in most of the cases, which was seen before further exploration however, which the entity seemed to learn from in the latter exploration. And the child wailing, seems to be more or less the entity itself, as yet again, a bait for the explorers, akin to that of the bulb of an anglerfish.

I've spent many a shower trying to speculate what caused the flash of light in the hole and what was at the bottom. Erghhhhhh

let's talk about what happened... in

EXPLORATION IV.

what happened? i agree with destructoid on an armed team, possibly enraging SCP-087-1 to perhaps turn into a worse entity, some sort of SCP-087-2.

the knocking could be an anomalous event, and is the spirits of the dead team banging, or perhaps 087-1/087-2.

the foundation doesn't know much, so , such is SCP. the staircase may not be endless, perhaps they should have someone parachute through the middle or something? lower a camera in there, creepiness, the effects of an open SCP-895(?), ect.

Also the "armed team" entering SCP-087 would not have occurred on the 4th exploration since the article explicitly states that the explorations were conducted by Class-D personal.