Insane Decay Of Mind - Steam Horror Game 2016 - Full Game Walkthrough Playthrough Gameplay and Ending (No Commentary Let's Play). This full game playthrough include all chapters, puzzles, full single player and ending of the game. Insane Decay of Mind is a first person horror game. You play the role of Katherine, a young girl lost in the eerie hallways of a building she believes to be her school. As she begins to realize that this labyrinth that she has found herself in, is slowly warping her mind; She must make her escape in order to regain her freedom. But freedom comes at tremendous cost. Leaving the labyrinth is not as easy as it seems as you are not alone, there are entities that wish to keep you from escaping. During your dreadful experience, you will meet beings called "Shadows", manifestations of your worst nightmares; you will have to subdue them as you continue wandering the darkness that envelopes you and, perhaps, you will achieve your freedom. Source -.