Okay, now I'm back DMing for the lead up to Moil. I need direct links so the players will know where to go, even if they don't know how to get there. So, I am having a servant of Acererak, a Tiefling Lich, setting up an Eldritch engine in the mortal world. It's in an abandoned dwarven city, Undermere, right on top of a trapped cambion (which was the reason why the dwarves abandoned the place).
My difference is this: this won't be finished, and though the lich finishes the Eldtitch engine it will be done quickly...resulting in what looks like an interesting puzzle.
Now what I want is a round room with a magic sigil in the exact centre, the sigil is the "safe spot" (though you make take Necrotic damage standing on it) as the room shifts around the players almost randomly, between the Dhadowfell, the Feywild and [hl=black]Pluton[/hl]. This is the ante chamber before the Eldritch engine and the encounter with the lich.
So the room around will shift, monsters may appear and if the players are in the room when it shifts they are more or less "stuck" until they can get back to the same plane as the rest of the party.
So I am asking for suggestions to disable this room for them to get to the next chamber. I am not very good at the actual logictics of puzzles, but this seems a very Acererak-y puzzle to have there.