The Half-Face Man and his droids have been stealing body parts for tens of millions of years.
The clockwork droids are unkillable, taking everything that the Paternoster Gang throws at them as if they've been gently pushed. It says a lot that Vastra, who was only ever frightened onscreen after the Whispermen murdered Jenny, sounds terrified as the group begins to get overwhelmed.
The Doctor inadvertently brainwashes Rusty into possessing murderous hatred for its own kind. The Doctor seems to understand the enormity of what he's done...
"I am not a good Dalek. You are a good Dalek."
The fact that Rusty was able to only see hatred and nothing else. Holy fuck, he knew the Doctor better than the Doctor knows the Doctor. You can truly see the shame in his face when he begs "No, there has to be something else there." Remember last week when we got more evidence that the Doctor isn't superhero material? This week, we got that and evidence that he's Anti-Hero material.
The Daleks have returned and racked up a huge body count in this story... some of it including their own kind.
The Dalek anti-bodies. Basically floating, mechanized eyeballs that activate whenever the Dalek has intrusive organisms inside its shell that liquify said organisms to be used as protein.
The Doctor letting a soldier named Ross die! He purposely gave him false hope before letting him DIE! And the worst part is that he doesn't show ANY remorse about, claiming that he was "already dead" and he was just saving the rest of them! Not to mention the thing he gave Ross that would seem to save him instead was a tracker so the Doctor could find out where his body would go! It was at that moment that some viewers decided that they couldn't even care much for Twelve. (At least until Series 9 and 10.)
The Sheriff of Nottingham does not hesitate to execute an old man who spits in his face by ramming his sword through his gizzard.
The robotic knights from outer space burn people to oblivion with cross-shaped beams for non-compliance. Not only is that frightening, it takes place in 1190, during The Crusades, which involved similarly gruesome acts of murder under the abused symbol of the cross.
The Sheriff is decapitated in a scene so shocking, it was deemed insensitive to contemporary events with the Islamic State beheadings and cut from the episode. It indicates the robot knights' shuttle fell on him and he was rebuilt into a cyborg.
Later, the Sheriff is knocked into his vat of molten gold by Robin Hood and bathed in it, killing him slowly enough that his gold-encrusted metallic hands are seen clutching to the side of the vat in a desperate and failed attempt to climb out before he died.
"Listen": In many ways, the entire episode is a subversion. It's set up as a "You should be afraid of this perfectly ordinary thing" episode like "Blink" (statues) or "Silence in the Library" (darkness). But in the end, the monster might not actually exist, and if it does it seems content to just be left alone. The episode even goes on to insist that fear is a superpower, something that makes the prey more powerful than the predator.
The Teller, and what it can do to you. If it thinks you're guilty, it goes ahead and feeds on that guilt, melting your brain down to soup in the process until it starts leaking out of your eyes. Victims end up with a massive dent in the top of their heads, indicating it gets part of the skull, too. Then Bank'll keep your vegetative husk around afterwards, on display, as a warning. If they don't want the husk around anymore, they Kill It with Fire.
Madame Karabraxos incinerates her own clones, taking sadomasochism up to a whole new level.
The Skovox Blitzer graphically incinerates a truant officer with laser fire. All that's left of him is a charred, severed hand with bits of fingers and the forearm crumbling off as it crashes to the floor. The horror is dampened when the murder victim shows up in the afterlife unharmed, and then it starts up again when he suddenly realizes that he didn't escape.
Missy gives her underling a very frightening Death Glare as though there is a conspiracy going on the Nethersphere, like an unsettling undertone of a false paradise.
The Doctor showing up at her school terrifies Clara because she knows that the Doctor is a Doom Magnet. When she says "are the children safe?" you can see the horrible possible scenarios turning in her mind.
Basically everything about the giant spiders. Writer Peter Harness was told to "Hinchcliffe the shit out of it for the first half" (basically, to make it scary), and it shows.
In-universe, it's shown the Doctor leaving and forcing Clara to decide whether to kill a baby or, potentially, the human race, shook her up significantly. So much so she tells the Doctor to leave Earth and never come back.
The Foretold is as grim and ghastly as you could ever expect from a mummy. And if you see it, you have a mere 66 seconds to live.
Somewhere out there, there is a cunning individual who knows who and what the Doctor is, invited him to investigate The Foretold in the hopes that they could reverse engineer the technology behind it, murdered a whole train car full of people to force the Doctor's cooperation, knew to seal up the TARDIS to prevent the Doctor's escape or rescuing of the passengers. When the Doctor manages to escape anyway, and then tries to track this person back to their source, they take the pragmatic approach and blow up the train. That person got away Scot-free and is still out there, and now knows how the Foretold worked and may have enough info to create their own version.
They took the series' infamous dodgy CGI and weaponised it. That, and what seems like an innocuous piece of fancy artwork, that turns out to be somebody's nervous system torn out and displayed on the wall.
The walls and floor appearing to melt and distort, coming towards you, then painfully dragging you into the two-dimensional surface. Or murals that appear to be realistic paintings of people facing away... then they start turning around and melting towards you.
To make matters worse, the Boneless use the horrifically distorted image of their victims for their three-dimensional appearance. Their dead victims. And that includes the woman whose nervous system was spread out on the wall.
If you still can't comprehend the horror, here are some◊ pictures◊ and a GIF◊.
Missy seems to have chosen Clara for something, as indicated by her appearance and words in the end of the episode. Her entire demeanor in the scene is really unsettling. Even creepier is the fact she is in front of a door with a window that looks like a Cyberman's eye.
"DON'T CREMATE ME!" So bad the BBC had to issue a statement.
The tombs with the skeletons submerged in water is rather disturbing, especially with the one located in Dr. Skarosa's office on display. And one of them moves.
The Cybermen rising from the graves, each one a poor soul who was tricked by a false afterlife into having their emotions removed. We see one remove their mask, revealing Danny's face underneath, pressed tightly in with cybernetics and scarring across it. And this is thousands of years worth of corpses that have been converted.
◊ It just screams "SOMETHING IS WRONG HERE".
