I really enjoyed this! This kinda stuff is right up my alley!
My only critique is that I didn't notice the monster chasing me at the end, so I didn't really have any urgency moving through that last section. Perhaps you could require the player to approach the opening it comes out of, or force the camera to focus on it when it gets near? Just something to make sure the player sees the danger (though my not seeing it may be unique, so take that with a grain of salt).
Even without seeing the monster, I really loved the atmosphere and the overall vibes I got from it! Good luck with your future projects!