do a spell check and clerical error check. Many are there.
Novel idea, not at all that bad as you sounded it would be.
Something worth pointing out is that, a Lot of very common words have been used which drop the medieval kind of flow of the prose. Use a thesauras and edit the story.
For eg. He got used to the light, can be he got accustomed to the light or another word for light.
Also at another place men had lost their Humanness change to lost their himaine or something.
Use a lot more difficult dictionary type words. Will give it a classy feel.
The main part, the climax sadly needs some more work as dosent live upto the hype created by the rest of the story.
Overall well composed and well thought, but that amateur waali feeling is still there.
Dude always review your work from 2-3 different views before posting.