In a survival horror game, how can we ensure the player fears their enemy without openly showing them how scary it is.

I'm thinking of a game where the player is pursued by a horrible monster; it's smart, deadly, and completely impossible for the player to defeat -- the only option is to escape. I'd like to harness the player's imagination to ensure the player is genuinely scared of the pursuing monster, so actually showing the monster is out -- once it's been seen the mystery is gone and the player knows what they're really facing.

Killing off the player quickly if they're caught is a simple measure to prevent a good view of the monster if they get caught, but given that what techniques are available to show that it's getting close and keep the player on their toes?

So far I know I can use audio cues, and I know I can make use of shadows -- especially if they're exaggerated and suggest varying features. Obviously the game's mechanics will also play a role, keeping the player under pressure, designing the environment to confuse, etc., but I'm trying to think of other ways to strengthen the suggestion.

Any other ideas or suggestions?

Audio, music and shadows were going to be my main suggestion, but you already mention them...

Have a second badass looking monster, that gets to see your monster, and is absolutely terrified of it?

Camera shakes associated with the monsters footsteps? Maybe dust shaken from the roof too.

Have lots of physics objects (barrels, crates) in the corridors you run through, that get smashed into by the unseen monster so that they fly in front of you?

Dolly zoom as the monster gets closer?

You could make the game music-less and use the screams or sounds of gunshots to cue the distance.

I don't know what the theme is. If it has to do with ghosts or the super nature you could have the environment starts to bleed, mirrors start to shatter, or have words or zombies start to emerge from walls.

If it is a huge monster then maybe the ground would shake.

If it is a fast monster maybe it would shoot darts and the player would see the near-miss.

In some arcade game where the player is supposed to dodge bullets, the game shows the location where a bullet would hit so that the player could dodge it before it hits. That kind of gameplay dictates where the player needs to be to be safe. It keeps the player moving. You could implement something that shows the trajectory of the monster's attack. Maybe a flash of light passing through the player's torso. If the player does not dodge somehow, the player gets sliced in half.

How about showing the things that this monster has destroyed? Other humans, who, the player's character knew before, just massacred, torn apart, and scattered around, might help the horrifying setting, especially if the dead ones were stronger than the player.

This is my thought as well. Don't show the monster, but show what the monster has done (proving that it is, in fact, a monster in the process).

If you can have something/someone the character's valued be destroyed in the process (iconic example: Aeris), so much the better.

Fantastic, plenty of good ideas there, thanks for all the input so far -- any additional thoughts are still more than welcome!

Have a second badass looking monster, that gets to see your monster, and is absolutely terrified of it?

I don't really want to involve multiple monsters, but I'd completely forgotten the (quite obvious in retrospect) idea of having other characters interact with it; I don't want other monsters, but I can use other victims!

Maybe dust shaken from the roof too.
Have lots of physics objects (barrels, crates) in the corridors you run through, that get smashed into by the unseen monster so that they fly in front of you?

I guess these can be broadly categorised into "environmental effects" of the monster, again a good way to show what the monster can do without necessarily having to actually show it.

Camera shakes associated with the monsters footsteps?
Dolly zoom as the monster gets closer?

Interesting, I was thinking about a "blacking out" effect as the monster actually attacks to help maintain the mystery if the player dies, but I hadn't thought about other camera effects at all. Definitely great ideas for a movie, but might they break suspense in a game where you're supposed to be the character rather than watching a camera?

Speaking more in theory, there's also a difference in the fear caused by the knowledge that we have of the monster.
In some games we know what the monster is like and we know where it is.
In some games we don't know what the monster is like and we don't know where it is.

Absolutely! I'm thinking more of the second situation. It will become abundantly clear to the player that encounters with the monster are deadly and that it cannot be defeated, but I want to keep the specifics of the monster a secret so the details are left to the player's imagination, and I'd like to keep them on edge having to second guess every turn of a corner or entry into a room not knowing if the monster might be there.

Even if the player does see the monster, this does not mean that the atmosphere is ruined. For instance, you can arrange the lighting to never reveal much of the monster, or you can design the monster in such a way that it slouches and has an indiscernible form, or it has a dark colouring.

Excellent ideas. I've realised I can look to some older classic horror films for inspiration, as they often kept their monsters mostly hidden because they didn't have the realistic effects needed to make something they could show.

I'm not sure if this helps, but there's a "Developer Session" from EGX Rezzed 2014 on fear and horror in games:

I haven't watched it yet, but thanks so much for sharing this -- I'll let you know if I find it useful!

...and I've got to run for an hour or so, but I'll reply to the remaining posts shortly! Thanks again!

How about showing the things that this monster has destroyed? Other humans, who, the player's character knew before, just massacred, torn apart, and scattered around, might help the horrifying setting, especially if the dead ones were stronger than the player.

Yep, seems like a good idea -- I don't have to stick to characters either, the same trick would work with props and parts of the environment the player is in.

Things such as only showing only limited view of the monster might help.

I like this idea, and as mentioned above it's one that was commonly used in older horror movies. Along with the use of shadows, fog, etc. I can show some of the monster without having to reveal all of the details.

If it has to do with ghosts or the super nature you could have the environment starts to bleed, mirrors start to shatter, or have words or zombies start to emerge from walls.

Zombies wouldn't fit, but the rest are good ideas. Reflections in broken mirrors might also be another way to give a scary view of the monster without having to reveal all of the details.

I don't know what the theme is.

I'm not sure on this myself yet.

Thanks again for all on the input!