Amnesia: The Dark Descent is a perfect combination of story, puzzle, and pure terror that is worth its fairly low price.
The game is played in First Person mode, though few weapons are available to you. Few, meaning not many, but not none, either. Many people make this mistake, you actually can defend yourself against the terrifying monstrosities that haunt caste Brennenburg. A lot of this has to do with an underrated physics system. Books, crates, goblets, bones, mostly everything you see can be interacted with. You can hide in closets after stunning them with crates. It is sometimes a bit unrealistic, however, in the distances you can throw certain things, however for the most part things act as they should. This physics engine, however, is best used in puzzles, something the Dark Descent is very underrated in. Some puzzles remind me of point and click escape games (many of them are) where you need to find some potion to open some door, and while I am a fan of escape games, the best puzzles actually seem like they com. from a true puzzler thinking game. You occasionally have to think about the patterns you see, read clues in the notes you find, and manipulate objects with out stashing them in your "inventory" to do things in the castle. Puzzles rarely feel forced, with the exception of the beginning tutorial stages, so the game stays fresh the whole way through.
That being said, the puzzles aren't very hard. They felt hard, however. I had no trouble knowing where the next gear I needed to get laid, however, I did have trouble forcing myself to go new places. Every door you open, every corner you turn is so suspenseful it took everything in me not to quit and start over again. The game is able to induce this horror in many ways, the first of which being the atmosphere and sound. The castle itself felt like it was falling apart (it is in some occasions), which creates vision obscuring dust. You hear your breathing, your footsteps, and muttering as you go through a fully sounded castle where the doors creak and random sounds echo as you lose sanity. Your only sources of light are your lighter, which requires conveniently accessible, but rare, refills, and tinderboxes which light torches, fireplaces and things of that nature. The light these gives off is very ominous and freaky. However, the atmosphere suffers greatly from horrid graphics. Many of the bigger, more important areas to the story are exceptions, but the hallways, bedrooms and cellars where most of the scares take place look bad. One thing that doesn't look bad, however, is the monster design. Many games build tension, but when you see exactly what you have been scared of, it is either too corny or non-original to continue scaring you. This is one field that Amnesia excels in. There are two types of visible enemies, both terribly disfigured humanoid things that move in disturbing ways. Everything about them is disturbing. In plain light they are just as terrifying as in dark. If there is one reservation I have about enemies, there is a third invisible enemy that wasn't scary or challenging to deal with. Without giving anything away, it is a supernatural presence that is chasing you by making flesh and blood that somehow magically hurts you appear everywhere. I am fine with this being a plot device, which it is, but it shows up too frequently and becomes annoying. Where Amnesia not only excels but pioneers in is its sanity system. This is the game changer, the reason this is a 9. You lose sanity in many different ways. Staying in the dark makes you lose your sanity. You could turn a light on, but that would alert monsters to your presence. Seeing monsters makes you lose sanity, as it should. (However, for some reason if you look at one too long it establishes a psychic connection that alerts it of your presence. I don't know.) Seeing supernatural events makes you lose your sanity. This is all well and good, but what going insane does to is worse. At first your vision just starts going in and out a little. At stage 2 this effect increases. At stage 3 all kinds of weird things start happening. The screen turns red, which has you frantically looking around for an assailant. Screams echo off in the distance. The worst is when you hallucinate an entire enemy, which leaves you running away as fast as you can, hiding, and then never seeing the monster, leaving you to believe it must be hiding around the next corner. It is very hard to get your sanity back.
The last crucial element us the story. Many elements are not original, but they are never corny. For instance, you wake up in a caste with Amnesia. Never seen that before. Oh wait, you find out you weren't really the best guy in the world to start with! Both of these seem like clichés, but the story is complex enough to make these starting points rather than the entire plot. You learn about yourself through self-written letters, the making of which will be explained towards the end. You also learn about the history of Castle Brennenburg, a mysterious man whom you first learn about in the first scene, some occurrence on an exotic expedition, and how the monsters themselves came to be. These are taught through notes, which are well crafted in that some of the smaller plot elements told in the notes are crucial pieces of puzzles. They are also told through flashbacks, which I didn't prefer because I couldn't read all of them and piece the plot together. Which leads me into my favorite part of Amnesia's plot you, the player, have to figure the plot out, it won't be randomly all explained in the end. The final small feature which should be noted is Custom Story, which allows players to download an easy dev tool to create little side quests for all to play, and there is a DLC called Justine which pits you in a diabolical game with some of the scariest looking things I've ever seen. (Search Amnesia Suitors). The two features are nice, but don't really extend the lasting appeal.
Overall, Amnesia's spectacular horror techniques make it a top of the line horror game, while puzzle and plot elements make it a complete masterpiece. Graphics hold it back a little, but they shouldn't take you away from the game. For 20$, often less on Steam Indie Sales, you'll have a hard time finding a better horror experience.