Dream Questing as open table play: it’s been done, right?

I’m going to pitch a campaign idea, and I want people to tell me 1) whether they’ve ever done anything like this before, and 2) how it went. Ok? Here goes:

Heroes adventure through a fantasy world (the usual: fighting evil, slaying monsters, rescuing imprisoned royalty, saving the common folk, overthrowing tyrants, wielding powerful weapons and magic, exploring the wondrous lands around them, making a name for themselves, etc.). But they aren’t firmly tethered to this fantasy world, because in fact they are from the mundane world, without monsters or magic or heroes or wonder. In their home world they are normal people, unimportant, but sometimes when they sleep they appear in the fantasy world and become heroes. And when they wake, they vanish from that fantasy world until their next visit.

To expand a little bit, the game would focus on the fantasy/dream world, never even depicting the mundane world that the heroes are from. The extent to which they can even remember their mundane lives will be down to individual players. Time moves on in the dream world when the heroes are not there, it persists somehow, somewhere, without them; but only the heroes have the power to make the world a better place, and the people of this world will suffer if they do not. It’s the GM’s role to make the dream world wondrous but also real, to put personality into the NPCs, to make the players care about what happens in this world that they are not fully a part of.

Ideally, this would be an open table sort of play, with players dropping in and dropping out as their schedules permit. Every session begins with the heroes arriving in the dream world, perhaps where they were before and perhaps somewhere different (the GM decides); every session ends with the heroes vanishing as they wake from the dream. That way, rather than using a single megadungeon, or a West Marches game where sessions start and end in a familiar locale, or some other conceit like Monte Cook’s alternate reality sessions, the expected shifts in party composition from session to session are explained by the strange magic that draws the heroes to this world in the first place.

The system used is largely irrelevant as long as it permits fantasy tropes and strange vistas. We could use Dungeons & Dragons or Pathfinder or Dungeon World or one of several OSR games or any universal system (Fate Core, Cortex Prime, etc.). If it’s relevant, then for the sake of argument let’s say we’d use D&D.

The idea popped in my head because of an odd confluence: I read the first chapter of The Night Land (in which two characters discover they share the same dreamscape) as part of my review of Appendix E, and I also read this review on Polygon for Kieron Gillen’s new RPG Die, a spin-off of his comic of the same name. Dream questing has certainly been done before in fiction (Lovecraft, Little Nemo, Alice in Wonderland arguably, and webcomics like The Dreamland Chronicles) but I can’t remember ever seeing it used in that way in a roleplaying game. But now it has occurred to me, it seems so obvious that I think someone, somewhere must have thought it up first.

So, readers, over to you. Is this like anything you’ve done before? If so, how did it work out?