I really like this, as an element that you can pop into any adventure I think it works perfectly, as there isn't really a hook right now. That's fine it could easily be created, or combined with some of the other entries to make for a longer story arc.
The only thing I'm wondering is what is making PCs go further down? What's the hook for them? What's driving them forward/downwards?
As previously stated really like the clear and clean layout, great style!