The Morgow rises!

Description

On the surface, Bosbradoe was a quiet Cornish fishing village. But underneath, in the damp and fetid darkness, in tunnels still wet with their slime......horrors were stirring.
People were disappearing, land was subsiding, the very earth was shaking in terror. The Things were on the move. Slithering and crawling.....nothing could stop their relentless progress. The Morgow Rises!
Old Cornish legend or horrifying fact.