Radiant Citadel and Spelljamming the Ethereal

 So, while I think a ton of D&D fans are super-hyped for Spelljammer: Adventures in Space coming in the summer, we shouldn't forget about Journeys through the Radiant Citadel, the upcoming adventure anthology.

While I've found that I'm less excited about adventure books, given that I tend to prefer homebrew campaigns (at least as a DM, though I think probably as a player as well) the core concept of Radiant Citadel is one that I think has a ton of potential.

The Radiant Citadel floats within the Deep Ethereal plane - a region that I think there's very, very little content for.

The exact role the Ethereal Plane plays is a little nebulous - before 4th Edition introduced the Shadowfell, the Demiplane of Dread (a.k.a. the location of the Ravenloft setting) was considered to reside within the Ethereal. The Shadowfell combined elements of the Ethereal and the Negative Energy/Shadow Planes (in 5th Edition lore, you basically can't exist within either the Negative or Positive Energy Plane, but in older editions these were basically just elemental planes).

The Ethereal seems to play a similar role to the Astral Plane as the "plane between planes," but while the Astral connects the Outer Planes, the Ethereal connects in the Inner Planes.

But it gets more complicated: in Forgotten Realms lore, there's a Fugue Plane that is kind of in the Ethereal, and it's here that the souls of the dead wait to be taken to their proper afterlives (generally in the Outer Planes,) and is where gods who are sort of judges of the dead hang out (also where devils hang out and offer to find a place for anyone who doesn't have a god to claim them - FR lore's not really kind to the irreligious).

The Ethereal is also sort of odd in that it has the normal spatial dimensions and temporal dimension, but then there's also the "border" and "deep."

In game mechanics, the border ethereal is basically "just to the left of reality" that usually is how you can do things like incorporeal movement. Ghosts, for instance, can slip into the Ethereal, and relatively low level spells like Blink let you slip into the Ethereal.

What I find interesting about the Radiant Citadel is that what we've seen of it suggests that travelers come and go, with different crystalline structures docking with it, and myriad cultures and peoples mixing in it... which, to me, sounds not too dissimilar to Spelljammer.

Now, it appears that 5th Edition Spelljammer is going to expand the purview of its setting - while Wildspace is still around, and you can totally sail your Spelljamming ship between different D&D settings, this version will also see these vessels sailing into the Astral Plane.

And really, once that's opened up, you could go anywhere. Why not the Ethereal Plane?

See, I'd love to see the 90s weirdness that was Planescape, but I think that Spelljammer could provide the underlying structure to allow for more plane-hopping campaigns - rather than through portals, we'd be flying ships (though to be fair, those ships are probably going through portals).