I was watching a film of the Great Devoid last night, and it occurred to me that the sounds coming from the hole are much like Tain sounds; and that the pillar of light is essentially a giant Fetch spirit. Those tho thoughts clicked together; Tain and Fetch; the Spider World!
Could the Devoid actually be a hole to the Spiders Gods' dimension? It could certainly be "bottomless" if so. Also, is that how the Dwarves got to know the spiders, with them crawling out of that interdimensional hole?
I wonder if the Fetch know this?