The Pit and the Pendulum

What is this horror I have awoke in darkness Now a denison of this awful dungeon I creep forward To try to get my bearings Only by briefest light do I avoid the pit And when I awoke I was bound to the floor Prone and helpless to what lay ahead And then I became aware from up above There descended a swinging blade, inches at a time And then to my disgust, the rats came for me Climbing out of the pit, here for my flesh They chewed through the bonds the held me And I rolled free of the blade I had angered my captors and the walls began to glow Not stone at all, some kind of metal The walls began to move, pushing me toward the pit