Parallel Plane Dungeon Ideas(Material/Feywild)

I've been drafting up an idea for a dungeon encounter for my group and I've been getting very into the idea of a dungeon with the same floor plan that exists on parallel planes, in this case the material and Feywild, with the party shifting back and forth between the two planes to solve puzzles, circumvent obstacles, find treasure, and hunt down their enemies. I'll start by listing a few of the ideas I've already had, but I'm most interested in hearing about other DMs that have run a dungeon like this, or just any cool or creative ideas for the concept!

On a plot level, I like the idea that it is a Fomorian Vault or dwelling and the party will need to kill a Fomorian (or more) and loot something from them in order to shift between planes, ideally at certain locations. While other creatures would be confined to only one plane, the Fomorians are more likely to follow the party.

My ideas:
- A trap hall in which, on the material plane, there are only physical obstacles (requiring str/con/dex) while on the Feywild, there are only mental obstacles (requiring wis/int/cha).

- On one plane there is a wall/chasm/unlit passage but on the other there is a door/bridge/lighting

- In the Feywild, a cavern appears to reveal a pleasant cottage, filled with food and warm beds. On the material plane, the same cavern contains bones and evidence of a hag/hags.

- On the material plane, there is nothing but the broken remains of a tower, perhaps home to a Dragon, but on the Feywild, the tower still stands and is home to an Eladrin Wizard (or perhaps someone more nefarious).

- The party rescues a competent prisoner from a cell in the Feywild, but once they plane shift, she appears as a Medusa on the Material Plane. (could be used for other monster instead)

- The party falls into a vertical chamber that is flooded with nothing but vines and waterfalls in the Feywild, but has been strip mined and filled with elevators and mining equipment on the material, through which the party can climb out.

- A room contains a large mirror reflecting the other plane, and perhaps revealing a large monster lingering in wait. A smaller hand mirror with the same effect can be found elsewhere.

- A room on the material plane contains a pair of skulls, one made of crystal and the other of gold. Somewhere in the dungeon, the party also finds a circlet as loot that can be placed on either skull. Doing so invites Fey from the Summer (gold) or Winter (crystal) Court into that room in the Feywild. In the subsequent room (also Feywild) a path is either melted (through which the party can swim, getting treasure off the floor but also attacked by marine life) or frozen (across which the party can easily walk).

- A room on the material plane contains a sphinx with four riddles on the wall. In the Feywild, assortments of plant or animal life are in the same place on the walls instead, and a fountain exists instead of the sphinx. Placing the right plants/animals that answer the questions into the fountain awakens the Sphinx on the material plane.

- A room contains a treasure chest on the material plane. On the Feywild, the same treasure chest appears untouched, because it is actually a mimic.

- A trap contains a poison that inflicts damage every minute while in the Feywild, but has no effect on the material. The anti-toxin exists in a separate place, also on the Feywild.

- A Green Knight assists the party in the Feywild, but begins turning to wood if shifted to the material plane.

- Magic idols on the material plane which have particular effects on their surroundings in the Feywild, such as causing it to rain indoors, summoning strong winds, or awakening plant monsters. They could either serve as outright traps or puzzles, such as pushing an idol into a room in order to cause a ladder-like beanstalk to grow in the Feywild.

Anyway, I'm hoping to hear if anyone has had any interesting encounters of this nature, or any sound advice on how to turn this hodgepodge of ideas into an effective dungeon.

A trompe d'oeil, from Pathfinder Horror. This creature steps out of a painting and hassles you. If you begin to catch on to it, it steps back into a painting, where it has perfect camouflage. The painting could be the portal between the Material World and Feywild. You have to defeat the trompe in order to get back where you belong and stay there. For extra complications (which you may not need), this effect is on several paintings in the tower. The trompe can move on either plane between paintings, so it could circle back behind the PCs to snipe at them, re-set traps, &c.

I ran two games like this. The first was a survival horror adventure where Demogorgon was terrorizing a small town and the adventurers had to chase him to his home plane, which they foolishly called the "Upside Down." The other was a grim dark medieval fantasy adventure where the players are all Revenants. They found a peculiar doll in their cell and when they brought it with them to the great cathedral, they were sucked into a painting to a demi-plane I called The Painted World of Armiamis.

Kidding aside, this is an awesome idea that I am 100% stealing. Alternative to the Feywild you could have them slip between the Prime Material and the Shadowfell, which would parallel the Upside Down quite nicely and be suitable for a Halloween adventure.

I'd check out a let's play of the Dishonored 2 level, "A Crack in the Slab" (I think it's near the endgame) that I'm sure would contain a lot of ideas. Main thing of course is to give the players lots of reasons to want to shift back and forth between the planes, and have each have different kinds of risks and dangers (not just different monsters, but different types of challenges entirely). Or have objectives be completable in either dungeon but with different consequences in each.

Oooo I love the idea of a parallel dungeon. That’s fun.
I might have to steal that.

Clckwrkhack said:

but I'm most interested in hearing about other DMs that have run a dungeon like this, or just any cool or creative ideas for the concept

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In my megadungeon, I've got a large cavern where the feywild and the material converge (inspired by the Genesis Cave from the Wrath of Khan). Actually, there are two such caverns. One is summery, the other wintery. They exist in no small part as a justification for the endless parade of wandering beasts throughout the dungeon.

I've been tempted to plan out parallel planes (feywild and shadowfell) like you describe, but just the material plane of a megadungeon is a lot of work.

Clckwrkhack said:

I've been drafting up an idea for a dungeon encounter for my group and I've been getting very into the idea of a dungeon with the same floor plan that exists on parallel planes, in this case the material and Feywild, with the party shifting back and forth between the two planes to solve puzzles, circumvent obstacles, find treasure, and hunt down their enemies. I'll start by listing a few of the ideas I've already had, but I'm most interested in hearing about other DMs that have run a dungeon like this, or just any cool or creative ideas for the concept!

Click to expand...

Very cool idea. You may as well consider it stolen

Clckwrkhack said:

On a plot level, I like the idea that it is a Fomorian Vault or dwelling and the party will need to kill a Fomorian (or more) and loot something from them in order to shift between planes, ideally at certain locations. While other creatures would be confined to only one plane, the Fomorians are more likely to follow the party.

Click to expand...

Might be better to have locations where the planes "thin" and travel between them can happen, sometimes even by accident. This would allow the party to stumble across the trick of the dungeon, but might also confuse the hell out of them.

Clckwrkhack said:

My ideas:
- A trap hall in which, on the material plane, there are only physical obstacles (requiring str/con/dex) while on the Feywild, there are only mental obstacles (requiring wis/int/cha).

Click to expand...

I think it's actually better to use this as a way of explaining having a crap-ton of traps. An area (hallway/room/whatever) on the material plane is trapped, but the Feywild version is clear, allowing those who know the maze a way of traversing it without setting off any of the traps. Works even better if you also add the Shadowfell, since you've got 3 potential options for every route.

In addition, to complete the quest the PCs have to find several McGuffins. Each McGuffin is located in a specific area on a specific plane. Clues might lead them to the room or the plane, but not both (at least not from the same clue). Creatures (minions) should only have limited knowledge: either a limited area or a larger area on only one plane. Only the BBEG knows everything, and the only way to get it is to find him and defeat him (works best if the players don't initially know who's in charge).