To start, Dream of the Blood Moon is based in the Unreal Engine 3, so it has technical polish and spectacular graphics, which in itself is especially notable for a free game.
Technical details aside, Dream of the Blood Moon tells a story that is much more elaborate than you may expect from a horror game, and even involves some interactions with other characters in the game.
Another thing that makes the game interesting is that you don't just have to flee from a mysterious entity that is hunting you - you also have to solve a series of puzzles that will put your cleverness to the test.
Dream of the Blood Moon is a horror adventure that does truly bring the horror. The story and puzzles are great, but it's the game's atmosphere, combined with its spectacular visuals, that make it an experience that you'll have a hard time forgetting.