Think I broadly understand what’s going on, having shaded 47 cells - very well constructed!
No idea what the title means, nor its repetition in the preamble
I have three unclued entries, but googling the theme word has not led me to any suggestions for the other three
And what on earth is the Charybdis clue on about? I have a possible answer, but cannot make head not tail of it
Any hints gratefully received!