Those "Oh crap..." moments

Occasionally when you're playing a game, something will happen where you have to stop, take a minute and get slightly worried as to what is coming ahead.  These moments aren't brought about by the game being bad.  It's not "oh crap things are about to get worse", it's more "oh crap shits about to go DOWN!"

For the example I'm providing today, we return to the dungeons of Grimrock

Everything up to this point has been made of stone, then you hop down some stairs and BAM! oppressive metal prison walls everywhere.  The corridors seem darker, there isn't a natural light source in sight and as soon as you step through that door, all you can see are pits and ominous shadows.  On top of that, you get a quite worrying little message from your telepathic friend (not spoiling anything)

I stopped just past that door, so I don't know whats coming next, but it ain't gonna be pretty.