I think that Tolkien's ideas on light are so interesting, and you've touched on some of them here, namely the lust for light that seems to overcome so many of the characters. I also really liked the atmosphere that you create: the dead and dying insects in the cave, Ungoliant scurrying across Aman like a spider up a wall, the encounter between Melkor and Ungoliant at Lammoth. Nicely done! :)