The Shadowfell and Ravenloft

 As a 5th Edition baby, I remember watching Stranger Things and, when they mentioned the "Vale of Shadow" as the equivalent to the Upside-Down, thinking "that's odd! Shouldn't that be the Shadowfell? Weird that a series that is willing to be pretty explicit in its D&D references would have some odd off-brand thing." Then, of course, I looked into the history and found out that the Shadowfell, as a thing, has only been around since 4th Edition. It was apparently a fusion of the Plane of Shadow and part of the Ethereal Plane.

I actually love the concept of the Shadowfell, especially as a sort of balance to the Feywild. The Feywild is bright and colorful and full of energy, but not necessarily good, and the Shadowfell is bleak and dark and subdued but not inherently evil. I sometimes like to say the Feywild is Manic while the Shadowfell is Depressive.

In particular, I like the concept that the Feywild and the Shadowfell are parallel worlds to the Prime Material Plane - perhaps even thinking of them as "Secondary Material Planes." This distinguishes them from the Outer Planes or even the Elemental Planes, in that they're still physical, real places, but just a little less so than the "real world." But also, I'm a huge fan of the concept of a world that is structurally similar to our familiar world, but is distinct.

The first Zelda game I ever played (though I didn't really play through the whole thing until college, well after I'd played several others) was A Link to the Past. This game, the third ever Zelda game for the Super Nintendo, has you first play through the "Light World" before journeying to the "Dark World," a reflection of the Light World that was more sinister. Where in the Light World there had been a sun-baked desert with ruins, in the Dark World is a great swamp. In the Light World, Kakariko Village is a pleasant enough place (except that they think Link is a criminal) while the Dark World equivalent is a haunted ruin filled with thieves.

The Shadowfell, to my mind, ought to work a lot like this: the familiar turned strange and sinister (though, again, not everything there is automatically evil - and in fact, you could have a whole lot of Tim Burton-esque inhabitants who seem creepy but are actually quite nice.)

Still, I don't think that WotC has been 100% consistent on what the Shadowfell is like, exactly. In the DMG, it's described as being similar to the material plane, but darker, as I've described above.

However, in 4th Edition's Shadowfell: Gloomwrought and Beyond, the primary Campaign Setting book for the Shadowfell, the implication seems to be more that it's kind of its own whole world, with locations like Gloomwrought, which is a city that has no real equivalent to places in the Material Plane but is sort of central to any visitor to the Shadowfell. (Gloomwrought as a location is actually pretty awesome - ruined towers and walls periodically collapse, but then others rise up on their own periodically.)

The Shadowfell hasn't starred in any published 5th Edition adventures - unless you count Ravenloft.

Ravenloft was first introduced in the original Castle Ravenloft adventure back in the 80s, though Strahd and his castle were not, I believe, meant to be anywhere but your standard campaign setting. It was in the 90s that Ravenloft was made its own campaign setting, and places like Barovia and other domains of dread were separated out. As it stood then, the Demiplane of Dread existed within the Ethereal Plane.

The Ethereal Plane is a good sort of catch-all for locations that don't fit nicely into the rest of D&D's cosmology. Eberron, for instance, was created at a time when WotC was less interested in keeping its world interconnected. That's why Eberron comes with its own planes for elementals and celestials and fiends and such. To squeeze it back into the shared D&D setting, though, one suggestion is that the entire Eberron setting, including its various planes, is actually a bubble within the Ethereal Plane (I think I'd just give it its own weird "Crystal Sphere" in the Prime Material, though.)

Anyway, either in 4th or 5th Edition, the Ravenloft setting has migrated to the Shadowfell. Given that the Shadowfell is meant to be the domain of spooky undead monsters and such, Ravenloft being part of it makes a ton of sense. That being said, the overall concept of Ravenloft and the Shadowfell do have some huge differences - the Shadowfell (at least how I like it) is a mirror to the Prime Material. The domains of dread, however, are extracted from the Material Plane. My understanding is that there is no place known as Barovia on any existing Prime Material Plane world, because the Mists of Ravenloft took it away, presumably kind of mystically closing up the wound on Strahd's original homeworld.

However, there's another potential interpretation that could be interesting: perhaps the Domains of Dread are actually nightmarish facsimiles of existing places. Maybe when the Dark Powers steal away a Darklord, they actually create a false echo of their realm - or take it from the Greater Shadowfell, even - and plop that Darklord and the poor souls who came with them there.

What I think would be so cool about this is that you could then have your players travel to the real Barovia, which could be a thriving kingdom that has been free of Strahd's tyranny for thousands upon thousands of years. Maybe the true Castle Ravenloft was long ago taken over by some benign ruler - or even serves as the seat of some democratically-elected republic!

Adventures there could involve the darkness of the Shadowfell, and the Barovia that we all know from Curse of Strahd and the earlier Ravenloft adventures, creeping into the true Barovia. Maybe the Mists of Ravenloft are particularly common in areas that correspond to the Domains of Dread.

I'm very curious to see if Van Richten's Guide to Ravenloft addresses any of these cosmic questions about the nature of the Demiplane of Dread. I suspect they'll keep it vague, to allow DMs to make up their own minds about these things. But I think it would be a particularly interesting idea to suggest that Strahd doesn't even have the realm he thinks he has - only a dark echo of it, just as he's only a dark echo of the human being he once was.