Forget about all those action games pretending to be survival horror, this is the real deal.
Amnesia takes place during 1839 in a remote castle Brennenburg deep in the vast woods of eastern Prussia and tells the horrifying tale of Daniel, an English archaeologist. The beginning is very Memento-esque, Daniel has no knowledge of who he is or what's going on. Right in front of him is a letter instructing him to do a simple task and claiming that there is good reason for his amnesia. The letter is signed "Daniel, your former self". I won't go into it any further, but I will say that the story is intriguing, well-told and presented and has a few uneasy (understatement of the year) surprises.
Mechanically, this is a first-person adventure game. The puzzles are both traditional and in a more modern twist, physics-based. They are all fairly easy, but more importantly, they are completely logical and there's a purpose behind each of them. There's always context, not a single puzzle is there just for the hell of it.
But there's much more to Amnesia than solving puzzles. It is very obvious from the get-go that there's something strange going on. Creepy surroundings, odd noises and distant shrieks drown the player in a chilling atmosphere. Then, of course, there are the things that go after you. And there's no other words to describe them because they are unidentifiable. In brilliant Cthulhu fashion, you have to worry not only for your physical health, but also your mental well-being. As Daniel gets frightened by witnessing horrifying images, he loses control which has real gameplay consequences. The player is slowed down, the graphics become blurry and distorted. Prolonged exposition to Brennenburg horrors can result in temporary loss of consciousness or even death.
So you can never really tell what's after you because you can't look at it and if you do look at it, your vision will become so distorted that you won't be able to identify it anyway. And then it will kill you. You cannot fight back. You are unarmed. Your only hope is to run and hide. Run into a room, close the door behind you. Pull a few chairs or a desk to block the door or hide in the closet and wait it out. The mechanics behind it are quite good, by the way. In Amnesia, you interact with items by clicking on them with the left mouse button and then moving the mouse in the appropriate direction to move the item. In one frantic example, I had to rotate a wheel to open a gate while I was being hunted in a flooded basement. I'm whirling the mouse like crazy all the while I HEAR the thing behind me splashing through the knee-deep water as it draws nearer.
It's moments like these that define Amnesia: The Dark Descent, one of the best and truly horrifying horror games ever made. It's insanely clever in its fright because it never directly depicts much of anything. Its horror prowess is mostly suggestive, the fear comes from your own mind as it takes it all in and imagines the worst. In a time when horror films and games are nothing more than action gore-fests, Amnesia does it right in an all-out attack on your psyche.