The concept is eminently game-able and sounds like a hilarious good time! I get some Fallout mixed with Addams Family and strong Tim Burton vibes from this. The Crown is a really cool item and so fitting for the tone of this adventure. I might play this over Halloween, but the one thing I might add would be some time pressure. Would it make sense if the party of knaves' bodies were falling apart or something to push them to a resolution? Or perhaps the Lich is about to finish conquering the outside world?