That's a very effective cover. Great idea!
Pretty small type for an A5 booklet. Great typeface, though. What one did you use?
Beautiful presentation all around.
This feels very mythic, which I know is a big part of His Majesty the Worm. This would take a little bit of work to convert to other systems, as some of the ones you reference here don't have obvious counterparts, but I suspect this adventure can be used in a lot of other OSR games to great effect.
Well done.