Pretty impressive for a first!
I like the style, and the atmosphere, but I think you could work a bit more on guiding the viewer. It took a while before I realized her voice was the problem - thought the first key was a razer, and towards the end I'm not sure if she greets the monster in naivety, or raises her hand in fear? Does the monster try to kill her, but give her a voice instead? Or only attempt to help her, and the machine misunderstands and kills the monster...? And why were they embarking into the pit in the first place? In search for her voice? Something else? Did the robot decide to help her? The 'thoughtless' bit above makes it seem like maybe it had no reason after all.
I like where this was going, but in the end it leaves me confused a bit. Uncertain of what I've seen; wishing it was clearer.
-cd-