I talked about villains (mostly human) and monsters (mostly non human). I feel there is another category in horror though, mostly environmental but really human vs something non sentient. What generally makes this effective is regardless of how dangerous whatever “it” is, humans are what make it even more so.
The Cube (Cube)
Built by humans but ultimately what makes it deadly is the humans in it. The Cube is dangerous, trap after trap after trap. The humans trapped in it need to work together or fall to it. Not surprising they pretty much all fall to it. Each one of them failing in different ways, and failing mostly to notice they have everything they need to get out.
The Cave (The Descent)
The actual cave doesn’t claim any victims, but it’s an important part of what puts the girls in a situation where they can be killed off. By the time the monsters show up the group has already fallen apart. They are tired, injured, have turned on each other, frankly they are easy to pick off by the time the “killers” show up. Some of the scariest moments in the movie are actually connected to their struggles with the cave, and not with the monsters in it.
The Event Horizon (Event Horizon)
Something satanic is in the ship, shifting it slightly from “other” into something else. The ship itself plays a very important role in everything that is going on though. What is in the ship couldn’t work in just any ship, it is the Horizon itself that is able to be taken over and kill the people that board it. It’s a ship that no one should want to get on.
The Sphere (Sphere)
While I am not the biggest fan of the movie, and loathe the ending, I like the idea of it. It’s not invented as a weapon, but it ends up being that and little more. The Sphere allows those that come into contact with it to imagine anything they want. The problem is the human factor. They all become paranoid and begin to imagine their worst fears picking each other off one by one. The Sphere shows that it’s the only thing humans seem capable of doing with that power.
The Box (Hellraiser)
It might seem like a strange choice at first glance. After all the box does nothing to you, it’s the Cenobites you need to worry about. However, without the box the Cenobites aren’t an issue. You are completely safe from these creatures as long as you don’t call them to you, you call them to you by messing with the box. Once you’ve interacted with it you bring a group down on you that desires nothing more than to cause you what they consider beautiful pain. They won’t stop, they won’t let go, you’ve messed with the box so they want you. Even in the first movie the hero attempts to make a deal with them and it doesn’t work. She hands Pinhead the only prey to escape them and he turns and declares that it’s still her turn.
The Hotel (The Shining)
The great debate about this is if the hotel actually did anything to the man, or if the man was already insane. The reasonable outcome is regardless of if the man was already insane, the hotel (isolation) is still what makes him snap. Either way I find The Hotel a fitting thing for the list. Whether a haunted hotel of horrors, or just extreme isolation that drives the people in it insane, they all snap because of it. What was once a semi functional family falls completely apart once they decide to check in and stay at that hotel.