Journeys Through the Radiant Citadel will take adventures into the heart of the Ethereal Plane, where a once-forgotten city stands in radical contrast to the deep and unending nothingness surrounding it. Those with an interest in the multiverse have studied the Ethereal Plane's overlapping boundary, also known as the Border Ethereal. Those unlucky enough to get stuck in the Ethereal Plane can end up in the Deep Ethereal, a boundless and directionless domain of swirling mist and dangerous cyclones. Keep reading to learn more about this peculiar plane!

• What is the Ethereal Plane?
• Traveling in the Ethereal Plane
• Dangers of the Ethereal Plane
• Adventures through the Ethereal Plane
• Using the Ethereal Plane in your game

What is the Ethereal Plane?

The Ethereal Plane is a foggy expanse with low visibility divided into two distinct domains, the Border Ethereal and Deep Ethereal. The Border Ethereal exists as an empty parallel plane to the Material and Elemental Planes known as the Inner Planes. Here, structures and geographical features are mirrored but shrouded in a gray fog. This part of the Ethereal Plane is an empty echo of the Material Plane, overlapping but not interfering. 

The Deep Ethereal lacks these orientating reference points, with only roiling mists churning in all directions. However, travelers of the Deep Ethereal will occasionally see flashes of light that can lead them to random locations within the Border Ethereal.

Traveling in the Ethereal Plane

An adventurer might seek to travel to the Ethereal Plane for several reasons. A creature on the Ethereal Plane cannot be seen or heard by someone on the Material Plane, allowing it to be used strategically to avoid enemies. Similarly, a creature in the Border Ethereal can bypass solid objects on the Material Plane. This makes infiltrating a location without proper defenses against extraplanar incursions all too easy for creatures that can travel between the Ethereal and Material Plane. 

Those brave enough to travel to the Deep Ethereal can use the Ethereal Plane as a gateway to travel the multiverse. Curtains of vaporous color are scattered throughout the Deep Ethereal that, when passed through, can lead travelers to regions of the Border Ethereal connected to one of the Elemental Planes, the Material Plane, the Feywild, or the Shadowfell. This makes the knowledge of how to safely travel the Ethereal Plane a powerful bargaining chip for purveyors of extraplanar travel.

Dangers of the Ethereal Plane

Though largely empty, the Ethereal Plane is not without perils. The endless roiling mists make navigating the plane a near-impossible task. Even when traversing the Border Ethereal, adventurers must take care not to become lost and find themselves in the Deep Ethereal with no way out. Beyond finding oneself lost amongst the fog, there are certain other dangers that travelers of the Ethereal Plane need to be aware of:

Ether cyclones

Ether cyclones are powerful storms of ethereal essence that rove across the Deep Ethereal. If they cannot be avoided, these twisting cyclones can impose significant setbacks on travelers in the Ethereal Plane. At best, getting caught in a cyclone will extend the duration of your journey. At worst, you could be hurled to a random location on one of the planes that border the Ethereal Plane, including the silvery expanse of the Astral Plane. Most ether cyclones don't physically harm adventurers, though there is a rumored standing storm known as the Keening Gloom from which no one who has entered has ever returned.

When traveling the Ethereal Plane, travelers with a passive Wisdom score of 15 or more receive 1d4 rounds of warning before suffering the cyclone’s full effect, which can be determined with a d20 roll after consulting the ether cyclone table in the Dungeon Master’s Guide.

Monsters

The occasional phase spider or ghost may take notice of a traveling party of adventurers, and nefarious creatures like night hags use the Ethereal Plane to intrude on the dreams of mortals. 

Due to the Ethereal Plane’s nature as a connection between other planes, most creatures found here will be travelers themselves, likely a wandering fey, fiend, or even a djinn from the bordering Elemental Planes. A traveler in the Deep Ethereal might also encounter a citizen or scout from the Radiant Citadel, the only known hub of civilization, culture, or trade within the Ethereal Plane.

Adventures through the Ethereal Plane

While the Ethereal Plane may seem devoid of good adventuring hooks, the introduction of the Radiant Citadel will soon open up this plane’s potential and allow adventurers to experience what it has to offer like never before. As a central hub for civilizations across the Material Plane, it's best to think of this new location in the Ethereal Plane as a way to connect diverse locations into one campaign. While we wait for Journeys Through the Radiant Citadel's release, here are a few ideas to incorporate the Ethereal Plane into your campaign.

1. Scattered and marooned: The cyclones that sometimes manifest in the Ethereal Plane are a great way to throw a curveball at your players. Consider an expedition gone wrong where your party's short trip across the Deep Ethereal sends them to the gates of the City of Brass, marooned on a distant planet in the Material Plane, or even the outskirts of the Radiant Citadel itself. Can the party adapt to the sudden change in location? Will they meet friends or foes in these strange places? How will they return home? 
2. A nightmare hunt: Night Hags are known to use the ethereal realm to sow nightmares into the sleeping minds of their victims. A group of adventurers could begin their journey in a town where the children are all plagued by horrible nightmares and end in a high-stakes battle with a powerful hag in the Border Ethereal. Maybe the town's nightmares gain substance in the ether, forcing your adventurers to literally conquer the fears of the children in the town.
3. A pathway to the Inner Planes: Much like the Astral Sea provides a connection amongst the Outer Planes, the Ethereal Plane serves a similar function for the Inner Planes. Incorporating the Ethereal Plane into extraplanar adventures can be an excellent way to help your adventures understand the internal logic of how the multiverse functions. Any plane-jumping adventure will see the party travel through the Ethereal Plane at some point, whether they are in search of the center of the multiverse or need to travel to one of the Inner Planes from the Material Plane.

Using the Ethereal Plane in your game

The first step in using the Ethereal Plane in your game is figuring out how to get there. Luckily, there are several ways to do this. The etherealness spell allows characters to enter the Border Ethereal for the purposes of magical travel or invisibility. The Deep Ethereal can only be entered directly through the plane shift or gate spell or the use of some other kind of magical portal. While there are no rules around traveling from the Border to Deep Ethereal, it stands to reason that creatures who can enter the Border Ethereal will be able to find their way to the Deep Ethereal with the help of a guide.

Those looking to use the Ethereal Plane as a means of infiltration should remember that it is still possible to be seen by a creature on the Material Plane that has true seeing or see invisibility active. Also, hallow, forbiddance, and wall of force can be used to prevent intruders from the Ethereal Plane. This means that if your party plans to go up against some magically gifted adversaries, they may well have the means to counter extraplanar incursions. Beyond infiltration, the misty expanse of the Ethereal Plane is also a great place for hiding valuables, as shown with the secret chest spell. Finding a way to rob a wizard making use of the spell could be another fun way to use the Ethereal Plane in your game.

A blazing light in the mists

It’s said that for those lost in the Deep Ethereal, the warm glow of the Radiant Citadel’s Auroral Diamond will provide a path through the misty surroundings to a place of safety. What new characters, stories, and adventures await remains to be seen when Journeys through the Radiant Citadel releases on July 19, 2022.

Michael J. Karr (@mikeyjkarr) is an elvish wizard trapped in the body of a human screenwriter. When they aren't trying to will magic into existence, they're busy creating stories through movie magic. You can often find them traversing the planes with their friends, but barring a very complicated spell of summoning, social media should work just fine.